I know the original sport lever and the pro lever are interchangeable and work with O2, C2, XC4 DH4 an E4 (allowing for the obvious open/closed system differences).

The mini lever works with the mini, M4 mini mono and M4 mono.

However, has anyone ever tried mixing from the two groups? Does it work or do they actually push similar amounts of fluid?

I seem to remember the press release at the time of the mini saying they were not interchangeable but has anyone actually tried it?

Morning crowd ever tried this?

Not tried it myself, but spoke to the guys from Hope when they first introduced the Mini, and they said it won't work due to different bore/piston sizes(and closed/open systems definitely don't mix).Using a Mini lever will give very long lever travel, using a Sport/Pro lever will give a rock solid lever with no bite due to insufficient leverage.Nothing to stop you experimenting though, they used a mini lever with a larger caliper for their Trials brake didn't they?

cheers, that's pretty much how I remembered it. Just wanted to be sure.

on similar note is a V2 lever interchangable with an x2 caliper?

I've got E4s and the old style M4's
The E4's have the pro lever and the M4's have the mini lever.
The only difference I can see in the caliper is that the M4 has a small and large piston on each side of the caliper and the E4 has the same sized pistons.
Rig one up and see how they go, I imagine you'd be able to get it to work but how efficient it would be I don't know