A cheap and easy way for a mock up is to use PVC pipe. Easy to cut and fit. It will give you the guide lines for laying the real pipe.
With the PVC you can bend it with heat from hot water, a heat lamp, hair drier , and even a 1000 watt flood lamp like you might use on a construction project.
You can use all the same tooling to fit the tubing and that sample can be taken to a bender to duplicate and you already know it fits.
What ever rider position you select the construction of the rider area is dictated by the rules.
The fact that you need the same protection for you is a plus because if you have the same cockpit construction and safety features for whatever power supp;y and level you evolve into over the life of the project.
You don't want any open ends in the tubing structure that can collect moisture from the environment and deteriorate it from the inside where you can't see it.
When you are done with the welding, sometimes the frame is filled and then drained with Linseed oil to give it a protective coating.
Another method is to interconnect all the tubes with a very small hole and pressurize it with dry nitrogen.
With a Schrader valve in 1 area and a gauge from a Fire bottle in another it not only keeps the moisture out but offers an easy crack check.
Argon as a backup gas will improve the welding quality also.
Use as many stock MC parts as you can because they are cheap , easy to fit, and as strong as you will ever need until you are really really going really fast .
ENJOY