I do not think it is too fast. I think it could be a tad bit slower but it will get the job done. You might have to make too passes though if it doesn't chop it up good enough the first time.
The TT is not available with a hydro, only a gear tranny. I used a Befco 66" tiller behind my TN but had to offset it to cover the right tire track. It worked fine that way but the TN had an 8x8 tranny and while it did work I just wanted something a tad slower so we added the 1920 and it took over the tiller duty.