Are you going to have a standardd shower head too? Because the benefits of having both are great. First, it's just the two of us as well and we still had the slide bar secured so it could double as a grab bar. You know just in case there's ever a slip. Then we also wanted the advantage of being able to adjust the height of the hand held. As it turns out, we can use both the slider & the shower head at the same time and boy is that wonderful! Basically with the slider you have more options for height and a secured slider can be a safety feature. Even if you don't need it now, for resale, that's a plus. I think for us it was one of those things where if you don't know you won't miss it, we did it for practical reasons more than anything else, then once it was in, we saw how great it is and were tickled pink.

Height of the rainshower head? I'd bring it down no lower than about 12" above the height of the tallest user. It can be a bit lower, but try to stay at least 8" above the top of the tallest user's head. Depending on the style of head you're using, 18" to 24" extension will work fine. Most true rainshower heads will not perform well unless they are installed parallel to the floor. So installing them on an angle, as they might be when coming out of a wall? You'll get some "rain" and some "dribble". There are hybrid rainshower heads that are designed to replace a standard head coming out of a wall, but they're not true rainshower heads. They usually have fewer holes to give a more forceful spray. They are "in between" heads. I've not heard of cleaning problems with metal hoses. I suppose hard water could bring that into play. I do recommend getting a hose long enough so that you can use the head to wash down all surfaces in the shower. You can also get additional head hanging brackets, they're only a few dollars each, so you can mount a bracket to hold the head at knee height for shaving legs, etc. Metal versus plastic? Some metal heads are cheesey, some plastic heads are fabulous. I've showered in all types of settings, from razor sprays that are painful to the gentlest of rainshowers. From one shower head to full-blown 24 head spa setups that make you feel like you're in a car wash. When I built my own shower, there were no limitations. My wife had carte blanche, we had no budget. All we did was we put in two heads on two valves. A 12" overhead rainshower, it was about $100 for the head. On the wall I installed a Grohe Top4 Relaxa head on a vertical wall bracket. I'm 6'4", my wife is 5'1". The head is easy to slide up and down as required. It can also be taken off the clip to be used as a hand held. I installed another bracket lower on the wall for my wife to use when shaving her legs. She can sit on a teak bench and clip the Top4 head into that bracket while she does that. I have two separate on/off supply valves, one for the overhad and one for the handheld. They can be run independently or simultaneously. They are simple valves, Temptrol. It's an excellent valve that will never cause problems. $100 for the rainhead, I think it was around $175-$200 for the entire Grohe setup, the Top4 head, the bar, the extra long hose, etc, about $200 for the two Temptrol valves. $500 for the whole shebang. No regrets. In a tub/shower combo, a rainshower head could be brought to the ceiling. There are plumbing kits that have chromed or other finish tubing that can be surface mounted on the wall to bring the water to an overhead rainhead. But mounting a rainshower head on a typical angled arm coming out of the wall? You might not get good water flow out of that. I have installed in-the-wall plumbing so that a rainshower head could come out of the ceiling in a standard tub/shower surround. The setups have had the standard wall tub filler and wall shower valve setup, I've usually installed a diverter valve so the water could come out of the wall shower head or the overhead rainshower head. Nothing ghastly about that at all. I would not have just a rainshower head as your only head. As other have mentioned, it's a very gentle flow of water, and does not do a good job of penetrating hair to rinse out shampoo. Mongo

Another Hansgrohe Raindance AIR handshower here. I like it very much. The "air assist" gives the flow plenty of power for hair rinsing. It only has three settings, though--fine for me, but you may be looking for more.

Looking at a house with the Master Bath shower recently redone with a rain head shower from the ceiling.I want to add a standard shower head from the wall with a hand held sprayer, both adjustable. It already has a thermostatic valve control. Would prefer minimal holes to drill with the new marble. Would have access to the plumbing through a closet. Any suggestions? All info greatly appreciated!