I've mentioned in other posts that the weight of the RFM is a big factor. At one time I had two different five foot RFM's on two different tractors. A lightweight 60" on the 16HP Ford and a heavy 60" on a 21HP Kubota. Both setups worked OK, paired that way. Out of curiosity I swapped the decks. Poor little Ford had a really tough time and prolonged use of the heavier deck would've killed it. The Kubota had a great time with the lighter deck. It seemed the Kubota barely noticed the mower it was pulling.