I have an RT11 and an RT13, they are simply amazing, the quality of the tilling leaves clients amazed. There is one issue with the design that I had to alter, on the back you have a flap, it's pretty heavy, there is a long 3/8" steel rod that goes through it and to the sides od the tiller, they have two small flaps that hold the rod in place, after hitting a few rocks the rod pushes the flaps out and the tailgate if you want to call it that will fall off.
I made my own steel covers and used two bolts, that was months ago and have had no issues with either since. I would guess we have tilled in the area of 200 acres in total and not one shear pin and we have done some pretty rocky ground.
I can till a one acre area taking my time in less than an hour.
The key is high RPM and go very slow, that will give you results like I have never seen, all three of my tractors play with these tillers, never a power issue (2305, 2520, 2720)
Personally I would pay a grand in a heartbeat as we till so much a third unit would be great.
When I get my unit(s) back this weekend I can take a pic of the flap I am talking about.
They work perfect with the IMatch if you have it.