I haven't sealed my fiber lips in 14 years of making baits and see no reason to seal them. You have to remember epoxy is a encapsulating material and it will stiffen the fiber to some extent, to what extent I don't know and I doubt anyone has taken the time to test the theory. Plus if you use the crankbait as it should be ie; deflecting off on rocks, trees ect the epoxy will be ground off the edges anyway. Hope this helps.
Jeff