Hello All
An update to this thread,  http://talk.newagtalk.com/forums/thread-view.asp?tid=395246&posts=10&start=1. I took some advice & added a piece of 1x1x0.100 square tubing to the 2x2x0.125 square tubing for a top brace. I was thinking of putting a piece of plate over the end of the 4x4 & tie it to the 2x2 brace, but I didn't want to close in the tube, it looks like that might be a good place to store some spare hose. I think that the suggestion of the 1/2" plate was overkill. The main frame is 4x4x0.1875 tubing, & that supports a 500 gallon tank full of water. 

Reason for edit: Typo.