I have a 7 1/2ft NH sicklebar moco, and the Massey 165 doesn't feel it unless you're in 6' high oats or something, my limiting factor is rough ground, or in cases of smooth ground sicklebar speed... I've been tempted to gear up the PTO drive on the moco so I can run less engine RPM, a higher gear, and still keep the moco running at 540. I'm looking to upgrade to a 9' at some point, still debating on disc or sicklebar... I do get a lot of lodged crops that a disc would certainly pick up better, but I don't know how much better.. maintenance on a sicklebar is MUCH cheaper, which is always something to keep in mind.
we have a NH 282 square baler with it's own engine, so I don't need much power for baling