I have two of these and they're great for the price - especially if you get all the important pieces - mainly the lower bolts to them attach to the containers. You can make everything else fairly easily, probably even the lower bolts too...
I've extended the arms to accomodate standard 8'6" and 9'6" containers.
here's a photo from this last weekend when I went to pick up a 40'er down in Baytown TX -- about 70-80 miles each way...
towing them empty they do have a tendency to wiggle, mainly downhill when they're pushing, but a quick (careful) pop on the breaks and the straighten right up. With 20'ers they pull just fine and aren't too bad at intersections (about the same as a full length semi-trailer). And with 40'ers they pull fine too - except turning at intersections they rear wheels cheat about, geez, 18-30 feet– basically the container is a vehicle with a 50’ wheelbase - so on two lane roads you begin and end right turns on the far left side of the road and might still need a bit more on the inside... and like someone else pointed out backing up is near impossible...
as far as attaching them it all depends on the ground the better the surface (harder and flatter) the easier it is... when separated and rolling them around with the casters they are "front" heavy (container side) and will tip/fall over if you're not careful. I've found it's best to only push by rolling the big tires and the casters tend act as brakes so I use a block and a crowbar to lift up one side to adjust the caster for direction. Get within an inch or two and it’s a cake walk from there…
and lifting I can do it by myself in about 20 minutes, yes it is like keystone cops running around, but it isn’t hard… there are air motors on all the pumps so you can use a bunch of air hoses and your truck to power them, but I’ve found it’s quicker just to pump them by hand rather than rolling out a bunch of hoses – remember you want raise the container as evenly as possible… And always carry extra fluid – they tend to leak at the worst time…
and be mindful of the weight – and empty 40’er is about a full load…
I’ve heard some states won’t let you register them – Texas will… and my guess is you might need permits for 40’ers in most states… here in TX technically I think you do, but since I tow mine with a tractor there’s a loophole - I can have a single trailer up to 59’ without a permit – if I used my deuce I’d need a permit…