I have a one piece longbow with a significant reflex/deflex design. I really needed 5" pvc, limb bend wouldn't allow the bow to fit into the 4" pvc. So, I purchased the 4" with a cap on one end and a threaded coupling and cap for other end (like previously suggested). I then took a heat gun and very carefully heated up the pvc. Once hot enough, I pushed on it, flattening it, which egged the pvc making it oblong. I did this to both sides. I did it with the caps on so each end is still rounded. Before gluing the cap on the end I sprayed expanding foam into it then glued it on. Once completed, I sprayed the PVC with textured Rustoleumn pvc/plastic paint. It works and looks great! Be careful heating PVC, emits a deadly fume.