Just got my Staytrem Bridge.. and I LOVE it. It's working better than the Mastery, at least on my Vintage JM! Mainly because of the string spacing (much better than on the Mastery, at least for that specific guitar), it feels more balanced and - espcecially - the low e string is not on the edge of the fretboard anymore.
"E to E string spacing is 52mm instead of the standard 55mm, this brings the strings away from the edge of the fretboard, this is another common problem solved"
Game-changer: on that guitar, YES
The radius is spot on - no way to adjust - but I like that since I always had problems with my Mastery even if I fixed it with nailpolish or whatever. Especially after playing a lot or - even worse - during gigs . Ok, hard stuff like superglue does help but I saw ruined adjustment screws (on one Mastery which I bought 2nd hand) - they were simply not adjustable anymore and I had to replace hem.
AND: it's FLOATING, there may be pros and cons about that but I'm fine with it!
Also, it's looks more correct on a vintage guitar (comparing to the Mastery).
The Mastery has probably a bit more sustain but I don't care!
My conclusion: The Staytrem "stays"

I don't want to offend anyone with this post. I only want to share my thoughts. Also, I'm still happy with the Mastery on my AVRI's ...