Clemson, I have several trailers with mobile home axles on them but I also run lowboy tires, not mobile home tires. If you know how to mount the tires they are very safe and efficient. The problems are with the tires stamped "for mobile home use only". And DOT can ticket you for using them.
On the hiller builds, lots of good looking equipment being built here. I took a shortcut when I built my gardening implements. On the Yanmars the bottom of the tranny/rearend is already sort of low so as long as you stay that high or higher you are ok. I have the reciever style 3 ph "trailer mover" as some call them. I insert a piece of tubing into my hitch and then weld another piece of 2 x 2 tubing to the first piece to create a "T" style toolbar and them mount hillers or cultivators or whatever I need onto the 2" T style toolbar. Tubing isn't expensive so I build one for each different set-up, never having to change anything from one to the other. And changing them out is as simple as pulling 1 pin and sliding that piece out of the reciever hitch. For a layoff plow to run my rows I built it out of a piece of tubing with 1 c-tine bolted to it with a small shovel, makes good rows in already tilled soil. I built another using a piece of tubing with a cultivator foot off of a H Farmall tractor, it has the adjustable angle for the sweep but I can mount a sweep, shovel, middlebuster...any bolt on plow to it.
I have the hiller parts but never put them together because I am in sandy loam on top of a hill, no drainage problems ever. I run a sprinkler and plant down in the furrow where the most moisture is.
I'm farming cheap with lightweight homebuilt implements that are light, change out quick and didn't cost a fortune to build. In fresh tilled soil, no rocks, roots or anything to get in the way, I can get away with it.