NECESSITY...is the Mother of Invention. Glad you had the fortitude, patience, and skills to attempt that modification. I will tear into anything but wouldn't have done that. I got my Ultimate Lowrider several years ago when they had a 1 time 20% off sale, and got the driver, driver backrest, and pass. pilion for $640. As a Christmas gift. I already had the Hondaline deluxe backrest for pass. and rear carrier. I have no doubt you will be able to fab a serviceable backrest for yourself. I offer the suggestion though, that you design a pivot to flip forward, or pulling the rigid bar out of the slot is going to get old real fast.
2003 1800C Black w/ H-K 3", PC III, Clearview w/s, Hondaline backrest, XM sat. radio, MB 12" shocks, Prog. fr. spgs., Wolo, SPyKER mod, Glen's gas cap, Paladins, Drag Specialties Popsicle pegs, K-N, blackened engine, Kury RTB, mirrors & r. boards, blue LED's, Rivco tach & risers, LeatherLyke bags, backrest bag, w/s tri-pouch, Gen. Altimax RT43, Mich. Cmdr. II, Ult. Lowrider, Showchrome grips. 12-18 VTXCafe Bike of the Month