I have these adapters and find them not doing it job good enough. If they had and the belt just where slow retracting I would have tried a set of new belts.
I experience that the belts folds in the adapter under use.
as you can see it folds between the "roll" and the adapter as well, but that I think is because of the angel of the adapter.
FoldingInChannel.jpg
If the adaptar has been angeled like the end of the rule on this picture I think most of the problem would have been solved.
Right now I see these alternative solutions
1. Try the seatbelt extenders from CarbonMiata
2. Get fabricate a better version of the Bossfrog adapter that leads the seatbelt in a better angle
3. Replace the Bossfrog Clearview maxx with a nother roll bar.
Another suggestions?