I purchased the G4 Simms last year with Vibram soles for the bow, not nearly as grippy as my old felt bottoms. (Disappointing )I have actually gone back to using my felt soles just for fishing the bow.
I turned mine inside out, rubbed dish soap all over them and inserted a leaf blower as I held the top tight around the blower shaft. Bubbles right away, just go easy with the blower as you don't want to,damage any seams. Hope this helps