a perry reflex is different than just "adding reflex" though. i always understood it as the effect of this particular kind of reflex, not as the practice per se. the bow is itself not reflexed, not in the traditional sense. basically, a reflexed backing is added so the thickness of the limb is divided between the belly half, which is largely normal, and the back half, which is independently pulling the belly forwards. the belly, not really being reflexed itself, is pulled on by the backing towards a reflexed position. the thing that differentiates this style is that a lot of the stress is held within the glue line. when the stress is focused on the back of a bow you may pull a splinter. when the force is focused on the belly you may get chrysals, crush the belly, hinge, break outright, etc. with the stress focused on a spot in the middle of the limb the chances of breakage due to that added reflex strain is greatly diminished.
sailordad, i wouldnt worry about the "extra pound per" stuff, that is a generalization. while it may be true, that isnt the most useful or effective tool to use as a way to begin the building process. just floor tiller the bow, then reverse string it even a tiny bit. when the backing is glued on in a reflexed fashion you should have a perry reflex. the perry reflex is a good way to use engineering principles to get a substantial amount more work out of a set up than would be otherwise possible. similar advantages can be had heat treating the bow, sinew backing it, just drying it in reflex, adding recurves...it is another of those trade off things. on a longer bow, the lightness of a thin wood backing may be more helpful than the reflex drawing potential of a (heavy) sinew backing, for instance. if you want to invest the time to add a backing and use this style, it can lead to efficient designs. SOM