After side-by-side comparisons with a mate also two-up on a Mutley through rain, I can say for sure that the mudguard / numberplate holder makes more difference than the crud-catcher. I had a very cool looking tail tidy, but in poor weather my pillion and my legs got covered in crap (even with the crud-catcher put back on). Went back to OE mudguard and the problem was solved - so it might not be the best looking but it works.
