Definitely go with a 6ft mower. I have a 4066R, which is the successor to the 1050, but with more HP and I run a 10ft brush hog. I bought a 6ft brush hog right after I bought the tractor and never used it as it was too small. I also have a 110 inch RFM and I just used it when I really should have been using a brush hog, but that has now been resolved with acquisition of the 10ft brush hog.
BTW when I had my 1025R, I ran a 5ft brush hog on it with no issues, except I could not steer unless the loader was on the front.