Nice to hear you're back at it! The fender idea you have seems a tad extreme. Got to thinking and may have a simple solution to move the fender to allow for chain stretch until a link needs be removed. Normally one bolt attaches the front bottom part of the fender directly to a frame crossmember. Simply make a few bushing/spacers different lengths, say 1/4 inch, 1/2 inch and 3/4 inch to barely fit over the bolt shaft and using a longer bolt just move the fender back with the spacer between the fender and the frame. Should be perfect especially since your fender doesn't support any weight and the two fender arm supports would loosen to easily allow the fender to move almost perfectly horizontally backwards to account for the spacer employed. They have to do this with your bracket system as well. I know you spent allot of time on those fender brackets and the welding involved. Sorry I didn't get on here sooner before you did all that.