Completely dependent on the limb profile. Mine works perfect with a powerlam, .006 taper, and tip wedges. To keep my glass to wood ratio good through the whole limb, I calculated out all of my various draw weights with different thicknesses of glass and tip wedges so that it usually starts around 16-19% glass in the very center of the riser, and 24-27% glass at the tips. They shoot great! (I make one piece longbows with 22" risers and very short active limbs)
But again, comes down to your specific riser length, limb shape, and limb profile, and generally a good amount of experimentation is required to get it just right.