Colawoman, for the va you have to do architectural drawings. And yes they are very picky but it really is to keep the contractors honest. They make them meet specs for ada and va. Yescv it does come down to inches and half inches because you need turning room in a chair or with a lift. Out shower in total is 10"long and 4'8" wide. Since it is at an existing shower space we were given an exemption on the 5' width requirement. But the inches do matter when you or someone else is in giving your pals a shower in a roll in chair. In front of the commode is 4"10". That is a waiver of the 5' turning requirement . However keep as much space as possible. Our bathroom is not that big and short of knocking out the outside wall or giving up our closet, this was out best option. They took it down to studs/block/dirt.
The grab bars are no longer considered necessary per the va inspector I spoke with. It depends on your pals. If they have no hand or arm use they waive them. But yes everything is about the exactness. Our shower entrance was tiled by mistake so it is now 35.5" not 36" . We signed a waiver.
Remember the idea is for when your pals is less mobile or in a pwc all the time so the height of things becomes very important. Even mirrors are measured so a pals can always use one. As I mentioned earlier, they are looking out for the vet.