I drilled through the cases, strengthened the insides using metal strips and used the existing Givi fixings on the racks, I removed the wedge shaped Givi top fixing to use the two screw holes. They're very secure. To remove the cases the rack has to be removed which can be securely locked to the bike.How have you fitted them to the Givi racks, have you put strengthening inside to take the weight and what locking mechanism have you got?
The top box is a Givi Maxia 3, 55ltr. It takes two full face helmets. I've used it on my last 3 or 4 bikes and never had an issue with a light front end, the key is to sensibly distribute the weight on the bike keeping all the light stuff up top. I also have Admore running/brake and indicators built into the box.What size is that top box? surely it must make the front end feel very light. I had a CBF1000 GT full touring kit, anything above 60/70mph you could hardly feel the front end on the deck. Made me very cautious especially in the wet and especially on roundabouts were the road surface is usually polished.