I might weld it as well...thing is if it was up to me I wouldn't fit a cage at all!... I don't plan on crashing; and it just weighs the car down!
I have been to 19 drift days with no cage and have not really seen the need for one...and before people think "they are just slow practices around an open field", these included twinning,80mph entry,solid concrete barriers and parked wagon trailers...
Quote from BDC rule book..
4 - Vehicle and Driver safety
4-1. Pro-Am cars must be fitted with a 4 point rear cage. This must include a diagonal bar
from above the driver's head down to the passenger side of the B pillar or lower section of the
passenger side rear brace bar.
Bolt-in or fully welded cages may be manufactured from
seamless T45 or cold drawn steel tubing.
Parts of roll cage within 150mm of occupants'
helmets must be fitted with fire resistant padding.
4-2. All cages regardless of material must have a main hoop (B pillar) from 45x2.5mm
or 50x2mm tube. 38x2.5mm or 42x2mm is permissible for all other parts of the cage’s
A 1mm manufacturing tolerance in tube sizes will be allowed.
4-3. Where used, all fasteners must be high tensile – ISO 8.8 or better and a minimum bolt
size of 8mm.
4-4. All roll cages must be either welded or bolted to the vehicle body using plates
that measure 5 square inches with a minimum 3mm thickness. For bolt-in cages a plate either
side of the vehicle body is also required. A minimum 3 bolts is required for the main hoop and
2 bolts for all other fixing points.