If you ever decide to install the OEM topcase for the GTS... Well here's a little thing to watch out for.
There are two long bolts that are responsible for securing the topcase to the plastic bracket assembly that comes with the topcase kit. These two bolts thread through both a locking nut and square fitting nut.
DON'T USE THEM!!!
They are IMPOSSIBLE to remove. Even with one person below holding the socket wrench and one above with a brand new, perfectly fitted screwdriver, the most we could accomplish is completely stripping the screw head.
I had to resort to small bolt cutters (large wouldn't fit the angle needed). And of course to get to the threaded part I had to chisle some of the plastic away inside the topcase. (no biggy as it didn't cause any damage and isn't visible).
But the smaller bolt cutters left my hands in serious discomfort.
A search showed others with the same issue, but no topic on the subject.
If you do get the topcase, I advise you take those two bolts to the hardware store and find a similar one with matching nuts. Virtually any will do. Just don't use the Vespa ones as they're over-engineered and probably not uniform througout the line.
(on the plus, it's probably the reason we haven't seen any posts on stolen OEM cases)...I'd love to watch a thief struggle with that one...