I have the two axle
BF fifth wheel, on the single axle
models the weight
is considerably less, but on the few singles that i have seen the tankage was mounted below instead of within the floor. Also the cold temp models were all double axle
I sure do like the way the double axle model tows, steady as a rock, no "hobby horseing" down the road.
I now have thousands of miles on mine and plan on putting on many more.