I have a stubby fitted to my 1150 and an RT pannier on the left hand side - took the lid and lock off my GS pannier so both panniers matched and one key fits all. Made up a bracket to locate the RT pannier with a few bits of metal found in the garage. Has been fine for last couple of years.
The bracket that comes off the left hand footpeg will need altering, the locating 'lugs' on the RT pannier are in slightly different positions. There are pictures somewhere on this forum.. try searching for 'stubby'