Campin Texan,
First off, The smaller the outside size is The thicker the wall MUST be to obtain the same strength.
Most of the "homemade" trailer frames are made of 2x2 x 1/8" steel.
One thing to consider is the weights of the steel you plan on using.
I don't have my book of weights handy right now or I would tell you the weight differences.
On my trailer frame, I used 2x3x3/16" for the main frame and 1 1/2 x 1/8 angle for the intermedeate crossmembers.
NO flex at all !!!!
Weight is only # 275 So plenty light !!
Walls are framed with 14ga 1x1 square tube!
I haven't weighed it again, But my figguring the steel in the walls only added aproxamantly 100 # more to the total weight.
Hope this helps.
Wanna Be

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~Elmer Davis
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