Lloyd,
Just in case you don't want to check the thread....here's what I did.
I took the base off the hump and sat it on the bike with the grab bar installed, then I marked the hump on the both sides of the bar. I reinstalled the base in the hump, then used a dremel tool to grind down the hump between the marks (I did it from the inside of the hump so that I wouldn't burn the paint on the outside) and repeat until the hump latches without contacting the bar. I found that an extra 1/8th in or so all around will give you good clearance without trimming so much that water will get inside.
The hardest part of the mod: the very first grind! I think you'll find that you are very happy with the result, just take your time! A couple of slips and you can really mess up the hump - so be patient.