I made them out of 1 1/4 inch EMT conduit from Home Depot, about $12.00 for a 10 foot piece and plenty stout for holding the tent. The O.D. is 1.5 inches so it fits a 1.5 inch die for bending tubing. The clmps I found are bolt together from a tent and awning supply. They are sized for one-inch pipe (1.315 o.d) but I was able to get them to fit the conduit okay.
I think the M101s look cool, but they just seem a bit small IMO.
Henry, what if you just put a rectangular tank across the front of the trailer, with a tongue box in front of it? The only downside to this is you might have too much tongue weight. I know I do. If I were to put one on, it'd be undernieth behind the rear axle.
Dan