So, I'm helping one of my friends get into archery.  He was lucky enough to have an old Bear in his closet that his dad used to shoot in the early 70's.  It is stamped 45#, and he went down to the local archery shop without me, and they gave him Heritage 250's...obviously way stiff with the 125 grain heads.  I shot his bow, and it shoots consistently 12 inches left.  
  I had him leave me the bow, so I could get it set up.  I had some Carbon Express Rebels 4560's and started out with a 165 grain head...stiff.  I ended up shooting a 100 grain insert and a 200 grain head before I ran out of extra stuff in my tackle box to tack onto the end, and it was still bareshafting a little stiff, but not horrible.  
  Today a put a stickon elevated rest to maybe be able to shoot a little wider range of spine.  I started out with the same 4560 shaft and 300 up front...spined weak with the new rest.  I dropped down to 125 grains up front, and the fletched shafts shoots 6" right, but now the bareshafts are grouping right with them.  Perfect group just 6" right.  All I did was add an elevated rest, and some beaver balls.
  So I went from 300 up front 4560's (30" arrow) which spine a little stiff to 125 grain upfront shooting 6" right, yet grouping with the bareshaft.  Also, I shot my bow, and its hitting dead on, so I'm thinking this is a tuning issue not my form for once.  What the heck is going on here?  Any ideas?

''Any ideas?''
1916.....stabow

The elevated rest is more forgiving of spine due to it's limited contace.  I've been using them since 1967.

More than likely due to the beaver balls adding weight to the string IMO. How much did you use?

It was 2 3" strips.  I'm still baffled that it shoots right, like its weak spined, but the bareshafts shoot right there with them.

The beaver balls won't do that.  Try cutting a quarter inch off at a time to see if they come over where they belong.

I think it's giving you a "False reading" with the elevated rest and here's why.  When you install a elevateded rest (stick-on type) it's going to push the arrow out away from the riser most of the time. Some rests are about the same thickness as the side plate when shooting off the shelf and some put the tip of the arrow farther left. If this is the case you would require a Weaker arrow. Check to see if this is the case.

Sounds like the amount of beaver balls is within reason. I've seen some guys bows with half a beaver pelt on the string, thats got to call for a weaker spine than a bare string or one lightly silenced. Keep at it you will figure it out one way or another.

ditto desertdude