The majority of competitions (nearly all) are shot using PL14/06 centres at 20 yards from the standing position. So, target height of about 1.4 mtrs should be OK. I should think that you will find everything else you need in Section 8 of the NSRA Rules, although you will have to hunt around a bit. You should note that the 4.5kg weight limit includes sight and glove (if used), there is a trigger weight limit >500g and all cards are scored using a .22 gauge.
Rutty