How many rooms and mini splits do you have? Do you run them pretty much all at once or selectively? What is the layout of the house?

1500sq ft, 3 BR. Closed plan, rooms are not open to each other. 2 outside units with 3heads each. No ducts in the house. I leave all the heads on 68*(i like it cool).

Try manually reducing blower speed manually or setting them to dehumidify mode. You might be cycling rather than going to the lowest compressor speed. You could try raising the temp in the rooms that you are not occupying to load fewer units running them harder. Heat and humidity moves very fast within a well-insulated structure compared to through partition walls. If you do not want to try that, see if you can figure out how to make a fur-down between two areas that otherwise communicate to serve as return airflow. That might be a LR and a dining room or one of those and the end of a hallway. Then you need a closet in that circuit to house the appliance. With a slab house, plumbing for condensate disposal is a problem for placement too.

I think that you are way above demand with your compressor capacity. Variable speed only takes you so far, maybe down to 30% of total capacity.

P.S. Cluster your ruining units on one outdoor unit when you can.

Why did you go for open cell? Closed cell rejects moisture better.

Have tried turning up different units and using dehumidify mode too. We are in 90-100 % humidity this time of year and have tried to keep up with it. They just wont do it.

Oh, and the reason for going open cell was $$$$ . I dod want closed cell for the added benefit of strenght but, everybody wanted 2 1/2 times the $ for the closed

You haven't said what your indoor humidity level is but I'll bet with a dehumidifier running, you'll be comfortable at a higher temperature setting than 68 degrees.

Just as a comparison, I have 51k btu or 4.25 tons in mini splits (7 indoor) to condition 2000 sq feet. (The house used to have two, 2-ton split units with condensers housed in one AHU.) I have a very leaky, poorly-insulated home. My house maintains lower than 50% RH with the Mitsubishi mini splits (~5 years old) with any significant cooling going on. RH is often in the low 40s and most often in the mid 40s.

Your home is surely better sealed than mine. How much cooling do you have in comparison? I think that the key problem is that you have too much cooling capacity for your house. That's why I was suggesting that you run fewer of them and gang up on one outdoor unit when possible.

I have higher humidity in shoulder seasons and run a portable dehumidifier, mostly at night, during those times.

You can retrofit supply ductwork into each room's ceiling using your attic. Return ductwork is a more questionable. If the air can circulate out of each room then you could have a single return somewhere in the house. If each room remains sealed most of the time then you'd need multiple returns.

The type of system you want is an ERV or HRV so that you aren't sending energy out along with the air attached to a whole house dehumidifier

I have 46K in cooling.. I was studying ERV's and bout had my mind made up. Then i spoke with an insulation guy and he told me i would be better off with a whole house dehumidifier that would bring in fresh air as well. Either way it is a good bit of money to me but, i have to do something. I am teally confused now as to which way to go

It is not clear to me if the OP has spray foam on the roof deck or the attic deck/living space ceiling. I assumed the latter since there are not ducts up there right now, but I could be wrong. In AC retrofit situations where attic ducts are installed, there is some advantage to insulating at the roof deck and sealing the attic making it into semi-conditioned space. (If there are no ducts in the attic, it is more efficient to put the attic outside the envelope. It reduces the size of the conditioned space.) Ducts always leak. New ducts leak and old ducts leak even more. Leaks induce pressure differentials and cause loss of lots of conditioned air. They turn your HVAC blower into a power vent if the ducts are outside of the envelope. If the attic is part of outdoors, putting ducts there is not ideal even though it is commonly done. If the attic is coupled to the living space, go ahead.

I am suggesting that a full supply duct system to each room may not be necessary for a whole house dehumidifier in this case. The OP probably has pretty tight construction so movement of moisture within the structure through partition walls will be much faster than from outdoors to in. I suggest that one supply duct and one return route might be sufficient depending on the layout of the house. It might be possible to harness the efficiency and quieter nature of a whole house dehumidifier with less fuss and damage to the home's envelope than might be thought.

OP, I am in NOLA with a mini split-only cooling system. My house is very leaky, but in the last few days my indoor humidity has been in the low 40s% or even sub 40% the last three mornings first thing with indoor temps in the low to mid 70s. My systems are off during the day and I have (3 of 7 of) them set to come on at 5 PM since I usually don't get home until after 7. I really don't understand why you can't attain similar, low, humidity levels. Do you have variable-speed compressors and blowers on your equipment?

@bw5then An ERV is in addition to a dehumidifier. An ERV mixes the two air streams air inside of a heat exchanger so that you lose less energy in your exhaust air. Without an ERV you will be placing a much larger load on your AC system because you are basically running your house with the windows open.

Know how the dehumidify mode works for your units. With my Mitsubishis, it is really poorly explained in the service materials and not at all in the owner manual.. I think how it works is that the system runs with the blower very slow and the coil very cold. Some cooling is expected in this mode and the controls allow cooling to some level that is pre-determined or to some level below what it is when the dry mode is started. I get the impression that a 3-4 degree depression from the start temp is allowed in dry mode.

I think that you should be really sure that you are doing everything that you can to reduce humidity with the mini splits alone. Maybe a call to the manufacturer is in order. I think something is missing. In addition, 46k in cooling in a tight 1500 sq ft home seems like a lot to me. Try running a minimum of units with the doors opens. Try starting dehumidify mode at a higher temp, 75F or above.

Keep in mind that an ERV alone will not dry anything out near the Gulf coast this time of year, it will just allow air exchange without adding humidity.

What are your humidity readings like?