IMO, I'd skip the 7 and get a twin spindle 8'.
While I have not ran either, those that have claim the 8' takes less HP to run.
To me, I cannot see any benefit of the 7' cutter. Claimes to take more HP for a smaller cut, sticks back really far so is not as maneuverable, and probably dont cut as even on rolling ground, and requires a heavier tractor and/or more weight up front than a twin 8.
Only thing I see a 7' useful for is a nice counter ballast for the FEL.
Now dont get me wrong, 7' cutters are fine. Just given the choice, I see a twin 8' offering so much more.