Now I have an issue with this mod. I was going to do it myself and purchased the platforms. I took it round to a guy I have used for years and knows his stuff (ex F1 stock car champion) and he said it was downright dangerous.
The problem is the perches have a different radius that the B7 ones. B7's have a right angle and the B5's a rounder radius.
Although there is a locator grove in the collar, there is a possibility that with heavy compression, it's possible the strut could punch through the platform. Take a look for yourself, I wouldn't go near it.
B5 on the left B7 on the right here
