Doc- I know in your Dacuda you mounted the bottle where the
passenger seat goes and not the normal trunk position.
The car I'm building probably won't have a seat on the
right either, so I could go either way.
Do you recommend the "seat" position for access to
controls?

I always mount my bottle behind the pass. seat, right where I can get to the valve.
The only thing to remember is to get the special "blow-off" vent fitting on the bottle so you can screw-on a tube to vent the blow-off out of the passenger area. Tech inspectors look for that venting system any time they see a bottle mounted in the pass. area. (You reall don't want to be sitting next to a 1000+ psi NOS bottle if it blow-offs into the car)
The other way to go is trunk mount with a remote valve controller but those are kind of expensive.
DD