Which design/layout gives the best strength?

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I have been welding with a MIG for the past few months and am making another project that will allow me to hoist a rooftop tent mounted on a roof cage/rack up to the underside of the concrete slab in my basement - giving me room to park vehicles underneath it.The tent and rack weigh about 150kg (330lb), I am putting the tent on a rack which I built today from Square Hollow Section 50mm x 3mm however I am wanting to brace the rectangular frame in the centre of the structure for added support. I was told by a friend to put the bracing on the diagonal making triangle shaped areas in the centre of the frame as this apparently gives the greatest support.Can anyone here please give me a little guidance as I am completely green on these sort of matters?What is the best way of bracing for greatest strength?If it is on the diagonal where do I have the cross bars meet the rectangular frame?I have added a very rough diagram i knocked up in Paint. The dimesnsions are 1550x1800mm and the interior rectangle is 1065x1700mm.Any help would be greatly appreciated.Cheers,Dave Attached Images
Reply:Perhaps more of a "truss" design would give more strength. Google in  - "bar joist" - and look at that concept.Thanks,HoboLincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:I'd throw one diaginal in the center that turns the area into two right triangles. As this is only 2D we can't tell how tall the structur is. I'd go with HOBO to add a short truss to the frame as well. This will help with torsional flex. not sure if you can or not. It doesn't have to be anything huge 1" spacers and some sort of small stock even 1/2" round stock would do the trick.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger