Whoa.....an accident waiting to happen. 10 psig may not even keep the bead sealed to the rim.
Well, haven't had any problems. I may have 15 or so in it, but seems if there is any more than that in them, it runs on the center(at least looking at the tracks pulling out of the water).
All I have on it is the aluminum boat, I don't even trailer the motor, and 200# is probably a good bit of an overestimate. (I'll have to weigh it next time its out).
I honestly think I could run them with no air at all and be just fine, but won't be putting that to the test.
I don't do this with the ST trailer tires on my utility trailer, the unloaded weight and taller sidewall could lead to the tire popping off the rim. I pump up my 4.80x8 4x8 utility trailer tires up to inflation pressure too, because it's loaded weight isn't constant (and it probably weighs more unloaded than the loaded boat trailer) But for this extremely light load with a set weight, with very little possible side to side forces able to be applied to the tires from the load, and stiff, short sidewalls, I'm not sure the the bead could pop off without actually trying to.
It just seems to put such a pounding on the boat too, there's no other way to ease that either that I can see, as theres only one spring leaf, unless I added a lot of weight to the trailer or something.