Making the 10" f/8 out of Porsa tubing?

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If I ever want to have a finished and useful tube for the 10" f/8 reflector it ought to be soon. I have wasted years trying to be clever without much success so far. The folded refractor used black, Porsa System, square tubing. This stuff is held together with alloy-reinforced, plastic joints in a complete range of leg numbers or branches. The joints are hammered home with a plastic, or rubber hammer, to avoid cosmetic damage. Resulting in a remarkably stiff framework. 

You can tell how tough it is because of its widespread use supporting massive fish tanks in great numbers and sizes. Often simultaneously on tiers of tanks. It can be dismantled again but it not an easy task and liable to cause damage. I had to open up a couple of joints myself but it did not seem to reduce the stiffness, or tightness, of the resulting framework. 

One vitally important aspect is maintaining parallelism between opposing sides of the frame during the build. The joints are very stiff and will not bend to accommodate lozenges. This needs careful thought and some common sense designing and putting it together in sequence. Closing a joint, only to find you have completely forgotten the parallelism rule is a real bore. Holding the tubes with heavy rubber gloves can help as you hit the tubing in mid air and hope it will come apart. Sticking the tubing in a vice is apt to damage the excellent finish. 

The cost of making a 2m long frame with 16 cross tubes and all the necessary joints comes to about 1600 Danish kroner. About £160 GBP. The great advantage is neatness and having a completed, stiff frame withing half an hour of starting. Add the mirror cell, spider and focuser and it is ready to use. 

I was going to frame both ends and have more frames at each end of the saddle to avoid flexure compared with unsupported main tubes.

I should have put another frame in the middle of the folded refractor had I thought about it. Though the lack of  center reinforcing frame doesn't seem to affect its remarkable stiffness.