Well I've got a Dual (Rev G) and a Mark V. I occasionally use them in stereo, although most of the time it's either-or. Too much gear to lug around if I take both rigs...
I think they
can be made to blend very nicely and complement each other excellently. They might not do so automatically, but give it some time and
use your ears when dialing the sound. The Recto gives you the dark, loose, scooped sound, and the Mark V fills in the articulate midrange bite. It will be one of the most awesome sounds ever heard from Mesa amps!
Just some things to keep in mind, based on my personal observations.
Do NOT expect to
separately dial in the perfect Recto sound and the perfect MkV sound and then try to match them. It won't work. Chances are they won't blend very well and your Recto will pump out way too much Gain compared to the MkV (and be way too loud as well, especially if you got the Triple).
Rather, turn both amps on simultaneously. First try to make them sound as
close to each other as possible, then work your way from there. (There are thousands of interesting combinations and possible variations to explore!) Of course they will never sound
exactly the same, they will retain their individual characters, and that's part of the fun.
In fact, I would suggest getting a Dual rather than Triple. It should be easier to match with a Mark V tonewise and balancewise.