I am a brand NewB with a B6100D 4x4 as well. I just purchased the loader and am in the process of installing it. I too have the belly mower, which is run off of the front PTO, via a long belt, and is from a 7100 (probably identical to yours). But I cant have my loader and mower too.... sounds like having my cake and eating it too LOL. I digress, so i decided that a rear mounted PTO driven finish mower was the answer; until I saw how expensive they are. So I elected to weld up a 3 point hitch and weld it to the mower deck. I had to buy an old gearbox from a "dead" finish mower and with a little work converted a belly mower to a rear mounted 3 point finish mower. There is some work to it, but it appears as though it will work. The snow has just melted up here so I expect in the coming weeks I'll have an opportunity to try it out. I'll let you know. My point is that with a little engineering, and relatively little welding (easily done by your local welding shop if you don't weld) you can use the mower you have..... I just didn't want to have to explain to my wife that I was going to spend more money on another impliment for the tractor.....