The plan you have for using a tub / shower valve to run two shower heads won't work. Tub/shower valves assume there is no back pressure on the tub spout. You can use any type of pipe that's acceptable by code for your area. Be sure to firmly attach the shower stub(s) to a support so they resist the weight of a showerhead and the installation forces. You don't want to open the wall again to fix that later. In addition, the pressure balanced scald guard valve may be required in your area and is probably a good idea with a rain style overhead showerhead ( think about a scalding situation..) You will also need to look at the volume of water in GPM for the shower using both showerheads. Will you need to change the design of your supply lines, your drain lines or your water heater to accommodate the extra volume of water? Do the math first. I happen to think multi-head showers, like big soaking tubs, are beyond wasteful -- particularly when many areas are subject to drought. The amount of heated water that's dumped down the drain is crazy bordering on criminal.

well, good idea but here's the problem - the faucet for the main shower head is just inside the shower door and I can turn that on and not get wet when the cold water comes down and wait for the water to warm up. But to turn on the rain shower head (or the hand shower - each water source has its own faucet), I have to be standing at the end of the shower where the three water sources are located - so I'd get doused with cold water turning on the rain shower head. In fact, even after the water coming out of the main shower head is warm, the rain shower spits out cold water at first. So what I've been doing when I can't stand being dripped on by cold water is endure a dousing in cold water in order to have those incessant drips be warm. Not a happy solution. It drips all the time once it starts. It doesn't start until a couple of minutes have elapsed. It drips even if I've not used the rain shower head in weeks (I tried not turning it on for awhile yet it dripped cold water on me daily). I guess I do have a diverter (sorry, I don't know all the technical lingo) - I know that I just inside the shower (imagine a long shower with the door at one end and the bathing area at the other end) I have a faucet that turns on the regular shower head. At the other end on the wall, there's the faucets for the rain shower head (on the right), the hand held (on the left) and to set the temperature for all of them (in the middle).

I could just get a handheld on the sliding bar but would like a longer hose to reach across the stall to the bench ( longer than the standard 60 " ) Does the magnet on the waterpick hold well on the sliding bar ? I notice that Moen has the Engage Magnetix Hand Held Shower Head as well. Does anyone has experience with it?

My contract with my GC provides that I supply the fixtures and obviously the rough stuff as well since it has to work with the fixtures. However, at some point someone who understands technical plumbing issues should be doing the purchasing or telling you exactly what to purchase. When I was selecting my shower fixtures, my designer obviously helped me with the look of the fixtures but she also explained the difference in shower valve temperature regulations - thermostatic versus pressure balance and then I decided which kind I wanted. The shower fixtures you select would then determine what rough you needed and she was responsible for ordering those. In other words I selected the style and how I wanted the end use experience to be like but she was responsible for making sure that everything necessary was provided to the GC so his plumbers could install what I wanted. So although I was providing the fixtures to the GC, someone with technical expertise was guiding me in the purchase.