I had the same problem with my '04 1150GSA - with full panniers and a load of camping gear it would topple over the sidestand, plus, even at 6'2", I couldn't get it upright without growing longer legs !
I used a Touratech side stand foot extender. They are not designed for the Adventure as the sidestand foot is a different shape to the standard GS, however I 're-profiled' the centre of the sandwich with a die grinder and it fitted OK.
Then I added a 19mm-thick piece of alloy, cut it to shape and put it in the middle of the sandwich. I had to take more metal off the foot as it interfered with the centre stand when both were retracted.
It works a treat.
I'll take pictures tomorrow if you're interested.
The original is a lousy piece of design (or is it cost-cutting ?) by BMW. The Adventure sits 1.5" taller than the standard GS, yet they seem to have fitted the same sidestand to both.
Bob.