Yeah you are right. I should add two notes really.

Lock at the right ride hight. Easiest way is to just adjust the droop grub screws (do tenth cars have these? I can't remember). My ZX-5 is all the way upstairs.... way to far to go and have a look lol.

My other note, the ride height is from the point of the tyre the car is balanced on. Tyres have a rounded surface, so you need to add this difference. See diagram below to see what I mean.

http://www.glypo.com/general/cog/factor.gif

I will use the board tilt method but remove the suspension first.

I want to know the CG of the chassis so that I can understand how the suspension geometry moves in relation to the CG location.

This looks like the easiest way to do it:
http://www.longacreracing.com/articles/art.asp?ARTID=22

I got it from this forum:
http://www.rctech.net/forum/electric...ty-z-axis.html