Wow, what a gorgeous place you have there! With the way the kitchen ceiling height changes in dining area to the vaulted, I was not sure if that would look strange in your KD's design that goes all the way across the longer back wall. I just played with my app by cropping things from BB's peninsula plan to move stuff around. Here is what I came up with. You could keep a small prep sink under that one small kitchen window since the plumbing is already there, but I moved the main sink to the pennisula. I moved the couch to the other wall and removed one of the club chairs because I wanted to get furniture away from the slider. I'm not sure if a round table is a good idea or not, but just thought how nice it would be for games and also faces more towards the views and the TV. I am sure it is not to scale either. Oh well, just throwing this out there anyways to spark ideas. :-)

Outside perimeter (max length = 118”) support is adequate for countertops supported on four sides with depths less than 26”. For quartz countertops supported on four sides with depths greater than 26”, in addition to the outside perimeter support, every 36” additional front and back underside support is needed. Countertops supported on 3 sides (i.e., dishwasher design restriction), a substrate is required. For 2 cm (13/16") thick slabs that are less than 26”, a 2” x 4” substrate is required at widths greater than 24”. For 3 cm (1 3/16") thick slabs less than 26” deep, a 2” x 4” substrate is required at widths greater than 36”. For cabinets that overhang the support structure, like cabinets, additional support may be needed. Evenly spaced corbels at 36” or less are recommended for 2 cm quartz countertops hanging 12”-18” over cabinets as well as 3 cm overhanging 15”-24”. For 2cm countertops hanging more than 18”, or 3 cm countertops that overhang the cabinet greater than 24”, a solid substrate and support leg(s) or columns are suggested. Both 2 cm and 3 cm thick countertops may require half wall overhangs for service bars. Half wall overhangs less than 1/3 the depth of the top does not need any additional support. Corbels are necessary to support all other half wall overhangs at ¾ of the total overhang depth with a maximum spacing of 36”, and must be placed at wall studs or bearing structure. Acceptable support materials include ¾” plywood, structural steel, and 2”x6” materials. Particle board is not acceptable for support. Good luck

You need a minimum of 24” per person for comfortable seating. If your island is 80” that gives you 3 people along the long side. You could not have any cabinet at the end, the last 15”, and that would give you room for one more person, assuming that the end of the island is at least 39” wide. You just have to make sure that the person at the end of the long side and the person on the short side aren’t sharing the same leg space. Assuming counter height, the person on the long side would theroreticly take about 15” of leg space That means the island would need to be at least 39” (15+24) wide at the end to comfortably seat both someone at the end of the long side and also someone on the short side. It is nice to have a seat on the short side as it is easier to talk to people when everyone isn’t lined up in a row. Also, remember that if you are doing counter height seating a 15” overhang is recommended for comfort. We did 16” throughout the long side of our island and 12” at the end for extra clearance with an aisle, with the thought that we aren’t going to often have 4 people sitting at the island at once In reality it happens a lot and we probably should have done 15” at the end too, but it has been fine so far.

I agree, the Kitchen Forum would be more helpful for you. Can you reach across that island to wipe the middle of it? I like a big island, but that one, I'd struggle to reach the middle. With that post there, it does make the seating tight. And underneath the middle of the island is a lot of wasted space. Would you consider an alternate arrangement such as this one? I think the seating would be more comfortable, the island more usable and still be compact for your space. Of course it would be square with probably a round table and 2 chairs.