Looking great Dave  
Instead of cardboard stencils -I used Clear Contact on all curves and shapes,a lot thinner than cardboard and seal all edges as Tony mentioned. On all straight lines I marked with pencil and used Blue masking tape,sealing the edges the same. The pencil rubs off easily when dry with a pencil eraser.
What type of paint are you using,acrylic,enamel or water based enamel ?
I found using the Roller gave a great result - Cheap and no mess.
Kev

Thanks for your feedback and tips Kev. The contact idea sounds interesting and easier than cardboard method.. will have a think about doing it that way , spose I could use the cardboard as the template to mark the outlines when I sand back the cab. Is there any risk of removing paint (basecoat) when you remove the contact though?
Haven't thought about what type of paint to use as yet , need to reread what you guys have done .. so many decisions