Anyone have expereince with Yankee Hill Picatinny Risers, trying to decise on 3/4 or 1 1/4, I have 3x10 scope to mount, it came with picatinny mount/rings and I need to raise them

Can't comment on the YHM riser.

I use this one piece mount from Armalite http://www.armalite.com/ItemForm.aspx?item=EX0027&Categ...11-8859-bafe17a66e1e to mount my 3x10x44 scope on my AR.

If you're made of money, the Larue mount is one of the best one-piece AR mounts on the market. I have a fixed 10X scope mounted in it
http://stores.homestead.com/Laruetactical/Detail.bok?no=30

FWIW, I prefer the one piece mounts for AR15's. Using extra high rings still won't get the objective far enough forward on some scopes.
I don't care for rings on risers. The potential for movement is too great compared to a one piece mount.

Both of the mounts in my links are QD. The Larue can be removed and reinstalled repeatedly without losing zero. The Armalite isn't far behind.