PTO 27hp, ~2700# machine
I think a 6' should be fine. My tractor has similar hp (heavier, but doesn't make much diff here) and I'm running a 5' hog more because it was there and cheap when I was looking; I could definitely make use of a 6'.
I see no reason why you damage your 1250. I use a 6 ft Woods Brushbull with my Kubota L 3240. It has slightly less hp than your machine and works just fine. I cut heavy grass and weeds with the occasional small sampling. It may bog down some but unlikely to damage anything.
I've got a 231 that's down for repair and I was looking to get something else to just replace it since in hindsight I needed a 4x4 and didn't realize it. I wanted a 40HP but the prices here stick and deals get gobbled up in minutes.
The 1250 I grabbed as a bridge till I can find something bigger because the price was very good and I can get my money back out of it.
Got it hooked up and made a few passes on one of our fields and it was fine. It was the easier of our fields but it scooted through better than I was expecting. The 1250 is geared pretty low and is essentially a 16x16 speed and I cut in 10 and probably could have gone higher.
What does suck is the rear lift arm speed. It's so slow even empty. Especially down. I'll probably also swap the brush hog attachment pins to the inside. The tractor arms were so spread out that I had to really take out the movement so they wouldn't sway contacting the rear tires.