Fabrizio,
There are a number of solutions to the visability of the third brake light. Davw W posted one on this forum, Steve Simmonds sells a version also. My solution can be seen here

http://www.pbase.com/rsyme/luggage_case_clamp

I spliced a lead into the one to the light on the "cobra" and fitted it with a waterproof plug. It's simple then to plug in the light on the luggage clamp when using the suitcase.

I like your car's colour BTW!!

Cheers!

Robbie
2021 Plus Four -- Helga
211-WX-1433

"Fettlebodge"--A chief of the PaddyMogs