No I don't.
After working up loads (168g TSX) at 100 yds for my new custom Ritten Precision .30-06, went to the 600yd range to work up dopes for my VX-6 CDS dial. Never shot prone before or past 100 yds. Well, started at 200 yds and when I got to 600yds (12.5 moa elevation), my 1st shot hit the 3" center (x ring), than 2nd hit the 6" center (10 ring), than 3rd confirming shot was again the X Ring!
My scope is mounted dead centered and plum with the rail\rifle. When I aim, I concentrate on a level & plum reticle. At this time, can't see why I'd need a level on this accurate shooting platform!? gun)
Ted