Dave Brooks is a (very) active member of the UK Cobra Club (almost 5,000 posts @ 5 per day). Currently on his 109th DAX build, but one of the most helpful people around (anywhere).
http://www.cobraclub.com/forum/member.php?u=12
You should be able to search there for some threads on the hardtop, or start one and chat about how he fits it to something different to the DAX.
The RMC is very close to the original DAX, but a Harrison appears slightly more rounded across the boot (but looks can be deceiving).
But if Dave has fitted them to other brands in the UK, then he would be able to say how they can be adjusted.