Excellent feedback! Thank you all. It is good to here from some folks that have one and like it!
Be advised that one must first determine what one plans to cut and how quickly one plans to cut it before matching a tractor to a mower or vise versa.
Since you're in TN, I expect you will be cutting grass. TN is not TX and heavy grass cuts much harder than weeds and brush, tall or otherwise.
I'm in SE IN and I've been cutting heavy grass for going on 50 years with various tractor mower combinations. As previously stated, I would not consider a 5660 with a 7' rotary cutter unless both mower and conditions are light and/or I planned to mow slowly and probably add front weights.
I use a Woods BB840X, 7' rotary cutter with my M9960. With chains, the mower weighs nearly 1,600 Lbs. Much of this weight is well behind the lift arms. My M9960 ROPS with the 240 LB. cast iron front weight mount (but without the suitcase weights) is more than heavy enough to properly handle this mower on level ground but I would need the suitcase weights if I used it on some of my steep ground where I use other tractor mower combinations.
I usually mow as fast as my mowers will mow well and terrain permits. Unlike most, I keep my rotary cutter blades sharp like a lawn mower (cuts better and uses less HP and fuel). I usually mow with EPTO engaged on the 9960. The 9960 is a 90 PTO HP tractor and the 7' cutter is all that it wants when in EPTO mowing annuals on level ground. Yes, it would produce considerably more HP (higher engine speed) and torque at the PTO with EPTO disengaged but I could still choke it out in heavy grass.
More relevant, I use a Woods BB720X, 6' rotary cutter with my Grand L 6060. This cutter weighs a bit over 1,300 Lbs. with front chains only. I use this tractor mower combination on steep ground and have 4 front weights mounted on the grill guard. It needs the full set of 7 but mounting 7 would require me to remove the grill guard and install the front weight bracket. I do not wish to do this because I would need to R & R it each spring/fall when I R & R the mower/FEL.
The GL6060 uses the same 148.5 CI turbocharged engine as the M5660 SU but it is rated at 53 PTO HP in the 6060 rather than 50 PTO HP in the 5660. From experience, the BB720X is all that the L6060 wants much of the time and more than it wants some of the time. With stall guard on, it is common for the computer to completely stop forward motion to allow the engine to maintain RPM.
I would not consider anything smaller than an M7060 with a 7' cutter unless both conditions and mower are light.
Ask yourself what you plan to mow, how fast you want to travel when mowing and how heavy is your 7' cutter.
SDT