I just cut the rear fender for my Mototeck. I emptied the storage compartment, removed the hump and entire back fairing piece to expose the rear fender, figured out which wires did what and cut them...removed the lights and got ready to cut...
My husband and I didn't want to cut off too much either because I need the storage. We were able to cut the fender while it was still on the bike, holding the undertail up to the bike to gauge how much to take off (basically just eye-balling it). You'll cut in to the storage along the back some, but cutting it while it's on the bike was actually quite easy.
Once we cut the entire fender off, we tried mounting the undertail, realized that we needed to take just a hair more off of the back, cut and filed it again, then mounted with very little gap between the undertail itself and the storage compartment...
I've seen lots of pics of cut fenders that were done while off of the bike, but to save yourself some trouble of dismantling everything, you might want to try that...the entire process took us about 4 hours...the easiest part was cutting the fender with a hand saw...we just threw a blanket over the rear tire to protect it from the saw...
Good luck...
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