Hi George,
Did you get a pillion bracket with your order? I did on mine but had to elongate the hole to make it fit without killing myself getting the pillion bolt in. I kept the Corbin bracket on there as it was a lot thicker than the stock and I liked that...
Please qualify 'a whole lot of room'? 1/4"? More? On my Corbin pillion, there is about 3/16" gap now but I can push it down as I install the bolt. This shows how long these rubber cushions/bumpers are, eh?
Regardless, the over the fender part of your bags and the length of the rubber bumpers are the issues. I had the same problem with the stock Triumph bags (with an over the fender portion) and the stock pillion. I had to really push down on the pillion to get it to mount.
I eliminated the problem by going with Easy Brackets (the stock pillion mount bracket laid flat on the fender after because I removed the over the fender portion of the bags) and now have no issue with the Corbin even with the 3/16" gap.
Do you have more gap than this?
You have three avenues to solve this. Either remove the interference with the over the fender portion of the bags (i.e., Easy Brackets), change the over the fender 'settings' (typically they are laced, perhaps you can re-lace an eliminate much of the bulge?), or cut the offending bumpers down (or have Corbin do it). How many bumpers are contacting the over the fender leather?
btw, I took a 'large enough' rubber washer and double-sticky taped it to the back of the bracket to minimize fender scratching...
