Several ideas here that need to be thought about.

Read sfi spec you can have holes in tubes. The size of the hole depends on the diameter of tube. Mike, Monte's within rules.

There are many approaches to grounding. Floating grounds have their place and most of the time the term is misused. Many in the real electronic industry have different ideas. We used floating grounds in radio and tv. You have to isolate with test equipment. In the home ground requirements change every year.

If your negative battery bus is not tied to chassis it is not ground. Ground is related to earth ground and is made theough carbon in rubber tires. I could see where there may be benefits to using an isolated negative. This way no current is traveling through chassis. The main rail the crank trigger wire is in is a non current carrying ground, well actually if chrome moly a resister. Pretty slick, if you understand why you did it.

I have a huge disagreement with the railroad industry, where I work. They ground everything. Then spend millions on lightning protection. Because lightning looks for ground. But, when you got two huge conducters running for miles at ground potential, and you use it for signaling, you really have little choice.

Some day I plan a total rewire. I just don't like anyones stuff sold to wire cars. The people who do this have a limited electronic knowledge. I don't have the time or energy to do this the way I think it should be done. Some are nicer than others. None would hold up in the rail industry due to vibration. Oh wait race cars vibrate all the time.

Nice clean work Monte. I look at anybodies wiring and take issue, including my own. When you do this 24/7 and the public depends on it. You'd better be right. Always looking for a better way.