I did mine on my 1100s, fairly easily with some 6mm ally plate, only dropped mine by 30mm and 15mm forward, may not be enough for what you need. If you drop too much her feet will maybe hit yours.
I will have a look at the mountings on the GS and see if the ally plate I have left will be suitable, I am an engineer and have access to tools etc so may be able to help you.
Al.