Rollcage - How to?

How not to fail: https://24hoursoflemons.com/how-to-not- … inspection

Generally if you are a good welder you can install a pre-bent cage kit ordered from online (still a lot of work to cut and weld ect, but don't have to own a tube bender)  or you can pay to have a cage installed.   Paying for someone to build/install a cage is generally not cheap.  Dunno about san Diego, but Generally.  (Doubt san Diego is magically cheaper)

If you can weld and go DIY really think out your plan of attack to have space to make your welds all the way but still have the cage close to the roof ect.

Oh and since you said your a tech, someone probably needs to own a welder on the team, probably not the kinda thing you can borrow the shop welder for, you go through  a lot of gas and wire.

When we got our cage from Roll Cage Components, it did have some fish mouthed edges (many people have used Roll Cage Components for pre-bent cages). If they are missing or something happens, you can use a hand grinder, plasma cutter or even a tubing notcher. It depends on what tools you have. If you are not 100% comfortable doing this, I recommend paying someone to do it. This is one place you don't skimp.

https://www.ozhpv.org.au/shed.html
You can find a .exe file here that will print out a notch profile
based on tubing sizes, and intersection angles.
Then basic tools can be used to complete the fish mouth notch.

Link to file https://www.ozhpv.org.au/files/tubemiter.exe
It does not function in Freedom Units, though. If you are Metrically challenged,
I'm pretty sure you can find a similar program for your Imperial-based brain.

Added value edit: Article on notching tubing: https://www.kitplanes.com/tube-notching-made-easy/

We used a pre-bent, U-weld cage for our 1996 BMW 328i convertible from Rhodes Race Cars (Indiana). It was freight shipped to the SF Bay Area, California.

The main hoop, halo, and front down bars come pre-bent. The rest of the pieces were either notched on one end or square-cut on both ends. Also with the kit were six 1/8-inch base plates. Because E36 convertibles have HUGE n thick  rockers, I bought a piece of 24x24 1/8-inch plate and bent/fabricated plinths for the main hoop and front down bar base plates.

My order of installation was: Main hoop base plates + plinths, main hoop, halo, front base plates +2 plinths, front down bars, rear stays +2 base plates, main hoop diagonal & harness bar, then door bars, and finally gussets per the Lemons guide. I clearanced the driver's door and mandrel bent the door bars to flare out into the door to ease ingress & egress. I did not install a front down bar crossbar.

You'll have to be mindful about when is the appropriate time to fully weld or just tack weld a piece. Some parts are easier to fully weld BEFORE adding the next piece. For example, once the landing locations of the main hoop and front down bars were settled, I removed them to fully weld the base plates and plinths. Then they were tacked back into place.

Tools used:
Miller 211 MIG welder with 0.030" wire and 75/25 gas mix
DeWalt grinders - one for cut-offs and the other for flap discs.
Bauer (Harbor Freight) portable bandsaw mounted on a SWAG Offroad bandsaw stand
Bauer portable bandsaw mounted on a Hercules "chop saw" stand. (Game changer!).
Woodward Fab Tubing Notcher with a Milwaukee hole saw.
Milwaukee 1/2-inch variable speed drill
Digital Angle Finder
Manual adjustable angle (lockable)
Harbor Freight 30-ton press & SWAG Offroad 30-ton brake (to bend base plates)
.. assorted magnets, hose clamps, and ratchet straps. The latter was used to suspend the halo in place with its union on the main hoop tack-welded while the front down bars were fitted.

Working at a leisurely pace, it took me a total of about three weeks. The base plates and plinths were a pain in the azz!