Grasscutter,
I have a 3510 with a 7' finish mower on the back. Be aware that this size mower usually is a larger category hitch (wider, larger pins).
I went to my local machine shop friend and had him turn down a pin for me out of larger stock.
It is large enough for the mower hitch, small enough and extending inward about 6 inches with a collar. This handles both the diameter and width issue.
As for HP to turn, not too bad. Can't mow at top speed, but easily turns mower unless hitting 3-4' unmowed areas.
Oh, and if you trailer it with the mower up like I do (to fit on trailer), be sure to secure the mower well, as it will be heavy and tend to swing and sway the trailer.
Hope this helps.
-DiskDoctr
