[scotoap]

I make mine with plasticard sheet and angle sections, just superglued together.

Thats if you can not get the preformed undertray for your chassis.

Take an A4 sheet of paper to get the bottom deck or shell base actual shape and add what ever clearance to the bottom deck one that outline you require.

If its a very wet and dusty track you will be using then I use plasticard sides too with a polythene cover over the top, trailing out the back for the run off edge for saloon racing or the usual velcro for body to tray for buggy racing.