I have both an E55 and a V47 tech. Both are excellent. The E55 developed a fussy latch after two years, but I still use it when traveling far and/or with the wife. The SR357 is a no brainer. Compensates for a design flaw with the tail of these bikes, and works great with givi cases or without.
After running an E55 for a lot of miles, I convinced myself that the big E55 looked too large on the bike. I bought and began using the 47tech. Then two guys at work bought FJR's with E55's and I was forced to admit they looked like they came from the factory.
Note: If you buy givi new, buy from a reputable distributor. Givi could care less whether your gear shows up with all the parts. They deal with authorized distributors and don't really care about the rest. AMHIK. They're the best top case out there. Just go through revzilla or someone similar, so you get an immediate fix in the unlikely event there is a problem.