Baeliog Tractor using Sketchup

I have wanted to use Google's Sketchup (free 3D modelling program) to assist me in planning out models and terrain pieces. About 4 days ago I finally started using it. Does anyone here use it to plan out their custom models or terrain? If so, can you please share your experience. I am after tips and hints. AND I would like to know if you actually build things in your scale of choice (ie 15mm, 28mm, 1/56 etc) or whether you model them at a larger size (maybe 1:1) and then scale things down later.

Anyway here is what I managed to build. I did it more as a learning project. I am still working on it.

Zombiesmith's - Baeliog Tractor for the Quar

Note: The Baeliog was modelled on photos taken from the internet, and it is done to 28mm.