Need advice building K/BFS chassis

[Jordan2021]

Hi guys and girls, I'm looking to start building my K/BFS chassis but unsure what diameter tube i should be using as the only rule book I have to have is the DLRA but this is how they word it. Vehicles in classes where the existing record exceeds 175 MPH shall use the larger tube minimum requirements. but they do not state what the larger tube requirement is. can anyone shed some light on this for me please.

[Stainless1]

Jordan, the minimum any streamliner should have is 1 5/8 x .120... the rules for small engined vehicles is they can have 1.5 inch tube but even if the current record is under 175, by the time you are finished it might be over 175.... and if you raise it over 175 then you have to stop running...
Get a rule book.... Roll cages must provide 360 degree protection for your entire body...

[will6er]

The K/BFS record is already 223.071. (8/91)