Yes piking is knocking off a bit of length at each tip to gain a few pounds. I always start out longer than I need by a couple inches so I can "pike it" right before final tiller. For some reason I usually miss my target wt. by 3-5 pounds. I'm just kinda lucky that way I guess?
Adding a wood or bamboo backing will increase the poundage, but in some cases it's nearly impossible to do once the bow is tillered. It all depends on the style your after, a straight profile D curve longbow would be fairly easy to back even after it's tillered. On the other hand, a hybrid reflex/deflex is pretty difficult to back once the shape is glued into it but it can be done. I've done it a couple times with mixed results.