[asid61]

Your design looks pretty good. However, as others have said, you might face tipping problems even with what looks like a pretty sweet setup.
You can still use 4 modules on a hexagonal chassis I think.

A note about the swerve modules you have setup: I highly recommend using the swerve design from team 221 if you go coaxial. Basically, they sell a really nice looking coaxial that is already optimized for weight. Download the CAD and use those ideas in making your own coaxial swerve.
Mainly I suggest this because it's already super light and they have very nice looking plates that you can emulate. Do you have access to a CNC?