My John Deere 2305 and BX2660 are both the same, nothing needed beyond the built in shock absorbing effect of the belts and they do slip, just not enough for you to notice. I had a John Deere that did not have tight belts and I would smoke them on occasion; same thing on a RFM.
Ahh, so you're saying that the belts are slipping, enough to protect the gears and engine, just not enough for me to hear it or to see smoke. I hope that's the case.