This is a problem that I also have.......I have tried a couple different methods that I like but don't know if they will pan out in the long run.......have caught very few bass on the rig to date .....I have used the fnf sucessfully on several occasions to catch croppie though ..there in a pear shaped bobber that has a little twist lock thingy on it that is easy to adjust the depth with..so far I haven't noticed it causing any damage to the line...the little twitching action you use does seems to cause the thing to slip a little on the line.... another thing I have played with is tying the fly on a leader 18" or so with a split ring on the other end then tying a snap to the main line... how ever deep I wish to fish I tie another snap to the main line with a trilene knot I think its called and clip the fnf bobber to that snap then if you want to change depths I cut the line just below the bobber snap and move the split ring up to that snap then tie the snap I just clipped off to whatever depth I want to change to...your only making 1 tie to change depths......don't know if this will work for bass but both these work well for croppie...