Strenght of Square Tubing on a trailer

[Bluewater0650]

I am considering purchasing a type of three car gooseneck trailer. The question is the "main" beams of the trailer are 4" X 4" X 3/16", this seems a little flimsy to me. I measured them and they are 41' long then take a 43" jog vertical, then another 50" horizontal. Typical goosneck style,the welds are deep and well penetrated
I have included some pics, and would greatly appreciate any input

 

[Bluewater0650]

I guess I should have been more clear. Does 4x4x3/16 seem strong enough as the main support of a unit like this?

 

[Bluewater0650]

Thanks, for the input, very helpful group here