Joe

Yes I have one and occasionally use. Whilst giving a good estimate it all depends upon the “quality” of the shot hole and the shooter placing the gauge correctly over the shot hole. 
Regards
Joe

Hi Brian
Good to hear that your stock has some adjustability but with Anschutz stock design the breech to butt length is way oversized for juniors. A major failure in my opinion. This generally means the left hand is “close” to the trigger guard and away from the rifle CofG. One option I adopted was the use of the MEC Centra hand stop and inserted added spacers thus lowering the sling attachment point. 
Would agree your thoughts on moving the body angle might just give enough clearance. 
Keep thinking through the options and the solution will come. 
Take care and good shooting. 
Joe

I am not sure on present day arrangements as organised by NRA. However a few years ago when I enquired the problem was obtaining a site on which to place the caravan. NRA were facilitating the sale of used vans but a long waiting list for a site. 
Ofcourse all things may have changed in recent times. 
Best of luck in your pursuits. 
Joe