OK, I'm back. Sorry, I couldn't see back there with a light but I'm sure it's an Allen head bolt. I just
can't see it even with a flashlight, to tell you what size it is
(6mm?). You'll need to remove the seat, side cases,
the small rear cover (two bolts under the rear of the seat), and the side trim (long diamond shaped body panels on
either side). The side piece removes with one bolt under the seat, another at the rear top, and 3 plastic fasteners on the underside.
The front of it just pulls out from a rubber plug friction fit. The left side has the seat release lock, I just let it dangle when I installed the rack.
It's just too hot in my garage right now for me to do it for more verification.
Those are the only parts I recall removing for the install. I didn't need to remove the turn signals,
but if you can't get to the top of the bolt with an Allen wrench to hold it, that might be an option.
Sorry, when I started this post, I though I could be of more help.
Edit much later: It turns out that I'm even less help than I thought I was earlier. I finally found the (unofficial non-GIVI)
supplemental instructions that I'd used to install the SR410 rack. It turns out that the supplemental instructions replace the
#15 bolt with a different bolt. I'm sure I did that and I just used a hex head bolt instead of a socket head bolt. I'll attach
the supplemental instructions just so you'll know what I'm typing about, however I don't think they will help much with the
diss-assembly problem.