had the same problem with my ss extender too - you need to bang it a bit to get it on - I used a rawhide mallet but a hammer would do, now looks like the NN photo
I have just got an 06 GS sidestand extender for my 06 GS (funnily enough) and it does not fit very well, see below, anyone got one on their 06 GS?
Tried a search but no luck.
This is where paranoia starts to creep in and I start to think my bikes not an 06