Hi

few tips for you to think about.

Well To make the design process easier I want to chosse all the size gear Ill need to get it off the ground.
Design and build first. for 2 reasons 1. Getting the correct ones. 2 Saving on postage by ordering everything at once

In terms of my design, A plane is designed around engine and passangers, the same for a car in a nutshell.
CnC machine is the other way round. Biuld the frame as solid as you can... the rails, motors and sized around the frame, that why you should do it first

What are your thoughts on going bigger?
It goes up in complexity and costs, it a lot harder to get a big frame properly square, its easyer to get a medium size one accurate. Keep to a reasonable size.