I have LL bags exactly like Cokerb. With the front of the seat against the tank, and the rear fender stud/ acorn nut, it doesn't move hardly at all, so I too didn't feel the need to drill the threads just to accomodate a bigger pin. I use the 1/4" and they stay in place for the most part, however, I use a small plastic tie through the end loop to keep from losing the pin, just in case it comes out. EZ-PZ.
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