[MarkB]

Ideally folk should be using what is commonly known as ERW Precision tube as it's square rather than the horrible "black" stuff which maybe has one square edge to it.
Only mentioned it as I know someone who is "trying" and I repeat "trying" to make a chassis using the "black" rhs and he is struggling bigstyle..It's ok for most things but not really much use for a chassis especially if you want it to be straight/square.