I know, this is sorta the question only I can answer. Well today i picked up a 22' travel trailer camper frame with tandem axles, 8 ply tires, and electric brakes on all wheels. I can easily cut the frame down to whatever size i want/need. For regular mowing, the 12' i have is just a couple feet too short on days i use the big bagger on the Ferris. I am thinking this fall i'll have more equipment on board and i don't want anything left on the truck because i want the bed space available for leaves. I'm going to have a rear and side gates on the trailer, probably 4 or 6' on the side gate. All i need to get through it would be the Lawn Boy and the eXmark 36" so 48" should be fine, though i may have to unload one to get the other out thats probably not a big deal... i would only have to do it once a week LOL. Here's my "needs": Room for regular mowing equipment with baggers installed and everything. Room for above plus leaf removal equipment (push blower, dethatcher that mounts on front of Z, hand tools, box for tarps, etc). Room for a 24" wide toolbox like that fits in a pickup truck bed Room for gas cans and portable toolbox I have even thought of a hopper on front to dump grass into so i don't have the mess on the truck and have to tarp it (in this hopper the sides would prevent debris blowing out) and not have to empty it to do personal errands in the truck after work. basically i want a self contained unit that only requires a truck just to pull it and to haul leaves in fall. The debris hopper on front of the trailer can come off in fall since we'll be dumping to the truck, that will free up trailer space for the extra leaf removal equipment that will be on deck. I don't really want the whole 22' length of it, but don't want to short myself. i want to be able to still go places in the rig and not have to park on major streets like semi's lol. We might be keeping the 6x12 or trading for a 6x10 (the 6x12 is my parents' and they don't need that big of one, they rarely use one at all but when they do they don't need a huge one). Now, on the width- the trailer frame rails are 70" to the outside of them (box frame not channel or angle) that goes to the inside of the wheels. My 6x12 is more like 6' 4" inside the box, so 70" may feel crammed. In fact the Ferris with bagger may not fit there even. But, the trailer has brackets that were to hold the camper floor and they stick out to the edges of the tires which is 92" width. I can build around the tires and put fenders on them (of course) so most of the trailer would be 7' 8" wide, which is pretty good width! I'm thinking of doing that. it won't be any wider than the tires anyway. As for sides- I think i'm gonna make stake pockets and go with wooden sides maybe use two 1x8's so have 16" sides. i think that would be good. i have 12" sides now which seems fine, but 16" holds more mulch... so many choices. i guess i'm thinking out loud since i'm the only one that can decide how big to make it, but i'm open to suggestions and comments and ideas.