Quote Originally Posted by Coober View Post
So does the tube HAVE to be high-tensile steel and must it be welded in place?
I take it that it is necessary that the tube be a tight fit within the chassis.

Presumably this is only required if the bolt passes through both sides of the chassis.
High tensile is a bit undefined.
You will get mild steel up to about dia40mm where 25mm round drilled to take a M12 should be sufficient (per bolt).
High tensile is 350Wa and the starts at 45mm round.
For a shear connection, yes welding would be required but not so for friction grip.
I would advise all diy people trying to do this to rather speak to a structural engineer and get good info regarding this if you have no engineering background.