1-1/2x3x1/8 for frame?

I've noticed most of you are using 2x2 or 2x3 for their frames. I have some 1-1/2x3 that I got for scrap metal prices. Is there any reason that will not work as well, as far as overall strength or problems with the torsion axle or tongue connection to the 1-1/2" bottom. I do have a couple sticks of 2x3 that I could use in select locations if that would help but I am trying to keep it as light as possible but strong enough for off road use behind my CJ8. I weld but I'm a carpenter and I tend to over build when working with metal. Thanks Bob 
