I made the mistake of trying to start shooting NRA High Power Rifle with a Frankenstein Rem700VS in .308 Win. Had a gunsmith fit a graco adjustable butt plate and a fore end rail, mill for a stripper clip, and fit with iron sights. It worked... but it was *dang* uncomfortable.
Eventually came across a deal on a take-off 6.5-08 barrel, got it mounted up and fitted with a Sitman National Match stock... way better, but too many things and adjustments to keep track of. For NRA HP, you have one set of settings for Standing/Offhand, a completely different set for Sitting/Rapidfire (usually the opposite cant), and yet another for Prone/Rapidfire - luckily the last is pretty close to the same as what works for Prone/Slowfire (the 600yd stage). But for a new shooter... I never really did get the stock to fit me well in all positions. At some point... I went back to a plain old Service Rifle for a year or two, just for the simplicity until I got a few other things (eyes) sorted out. Then I started finding that damn, I could actually shoot thes things okay, and the adjustable stock on my Prone rifle made things really sing!
Last season I picked up a spacegun for XTC... I've got it all dialed in for Prone/Slowfire (and by extension, Prone/Rapids). Standing and Sitting are going to be... interesting to sort out. I know what I want (kind of), but this stock is even *more* adjustable than the last one (almost as bad as a smallbore 'Free' rifle)
Fitting my hunting/tactical rifles seems a whole lot easier by comparison, mainly because there generally are a whole lot less options for adjustment commonly used. Then again, 'field' rifles get used from some really odd positions as well ;)
When I mentioned be a bit outside the standard norm for size... generally, once I have a rifle really set up for *me*, most other people have a hard time using it. A lot of people can't hardly reach the trigger or see through the scope