For years I have had an in-line volume control on my shower nipple/head, when using a standard 3-valve tub/shower control. For water saving "submarine showers" (if you know what I mean). I usually got a little cross flow from cold to hot when turning back on from the off position of the volume control (water colder than normal). No big deal.
I'm installing a new Kohler Forte Rite Temp system on a new tub/shower unit. Can I still have a volume control between the pressure balance valve and the showerhead? The manual recommends against this, but if I have the same results as before, should be no big deal.
Also, what about installing check valves in the supply lines going into the PB valve? Would this help and should I go swing or spring?