It ought to handle it OK. I have a TC18 (HST) with a 60" RFM.
18HP (gross)/60" = .3 HP per inch
25HP (gross)/72" = .35 HP per inch
I can mow pretty fast. You can tell that the tractor is working to mow up a steep hill, but I wouldn't classify it as struggling.
I try to keep up with the lawn (weather permitting) and follow the "1/3 rule": Ie I cut when the average hieght of my lawn is 4.5" to get back to 3". It is supposed to be best for the lawn & keeps clippings to a minimum as well.