steve vai did indeed use the ibanez backstop.
its not as stiff as a tremsetter.
and since a tremsetter feels stiff, doing flutters, well forget about it.
vibrato isnt affected, unless you do very very wide vibrato where you go above and below the target note, then you'll feel a like a little click where the center of the trem is at.
and yes, i have a tremsetter, but not installed yet.
tho i've tried my friend's tremsetter equipped guitar.
and it does help if you like doing double stop bends etc.
my trem tho is decent, a schaller floyd, just want more stability.
and just make sure you really want a tremsetter in, cos you'll need to drill a few holes.
so yea, theres my reason why my tremsetter isnt installed, not enough wood
24 fret, H/S guitar, neck pickup slanted, so if i want the tremsetter i have to sacrifice my neck pickup.