the Minnesota DOT laws I went through stated clearly that 1000lbs of tanks and gas (weight not pressure) could be hauled legally in a non commercial vehicle. if you are associated with any business even something like towing the trailer with your work truck (with advertising stickers on it) on the weekends makes it a commercial deal and the fines are out of this world. even worse things happen once you get busted, they start looking at hydro dates and burst discs and so on. This happened to a local guy and though he got out of it the officer was a pain and actually checked up a few weeks later.
the average weight of an aluminum 80 empty with valve is something like 32 lbs (ish) which means you could carry just over 30 empty tanks. I'm sure none of them will be empty so better lean on the safe side and stick to the 25 range or less. Thats with 80's of course, if you dive say double steel 130's and use 2 aluminum 40's for deco gas your looking at enough tanks to outfit like 8 guys with empty tanks or more like 6.5-7 guys with full tanks.
Its always better to stay on the safe side legally, if your gonna push the limits at least have a really strong and impressive system for securing the tanks so if you do get pulled over and inspected for some reason the officer will be more likely to look the other way. Post a big label over the tank area with an OSHA warning and a contents label on each tank to really round out the setup. Its all about squeezing through the cracks at that point and a few dollars invested is better than a few hundred or thousand dollars in fines.
Trailers make great devices for hauling gear but coming from a former trailer dealership I like to warn people about overloading them. I have seen people get 4 grizzly 660 ATV's on a 2 place aluminum snowmobile trailer and brake the axle right out from under it going downt he road at 60 miles an hour. I fixed 2 fish houses (this is minnesota, people put wheels under small homes to drag out on the frozen lake at 30 below to catch fish) last year that were loaded to the brim with fishing gear and bunk beds and all sorts of misc stuff like tv's then they were hauled a mile out on a lake over bumpy ice at highway speeds. the whole axle and suspension assembly crumbled leaving these guys stuck out there. Both houses were the same manufacture and owned by brothers.
As a general rule I say dont exceed 2/3's the weight rating especially if you frequent bumpy roads, carry uneven loads, see excessive corrosive issues due to salted roads, or take the trailer loaded on the freeways. Imagine loosing a leaf spring at 65 mph on the freeway with a load of 20-30 improperly secured tanks...
also before taking extended trips or at least once per year depending on use make sure to check wheel bearings for wear and lube as necessary, under excessive loads or uneven loads this can really lead to some bad issues. A guy with a 7klb dump trailer came in having lost a wheel and drum completely going down the freeway in Minneapolis. the wheel nearly caused a pile up. the guy got the trailer new only 6 months earlier and took frequent long runs with it hauling an ASV RC100 (I think) and had never lubed his bearings and after checking the other wheels it turned out the manufacture didn't pack the bearings during assembly.
Of course those are extreme conditions but I must have repaired 2 or 3 dozen trailers in a year just because people didn't use common sense or establish a good maintenance system. Not saying your one of those people, I just dont want to have anything bad happen.
