I do something similar to Mark. I use cylinders but have one ball that I use near closer to the bow, just after the hull starts to narrow. This provides the same separation from the dock as the cylinders provide.
I just leave the all to bounce around on the foredeck. With a protected walk around with additional rails, it has never succeeded in bouncing overboard, even in seas that I've promised my wife we would never see again.
Actually, an outstanding suggestion! and pretty original.
I got a scrap piece of UHMWPE 2x4 to use as a fenderboard. Plenty strong enough and much better than wood on the boat. It doesn’t stain or rot and cleans easily. Lay it outside two cylinder fenders against a piling, works great.
Find putting some water in the inflatable ones really helps.
Carry full set for both sides. Mix of mostly cylinders and a few balls. Use a board when obligated to fender against a piling then two cylinders.