Wow, cheers JK! Now that you mention the brand name that was exactly what was mentioned to me - how do you know all this stuff!
I'm at the point of having over half of the body sanded back down to the black ribs but the problem is that the grid of black lines makes it even more difficult to eyeball the body curves. When I was doing the bodywork on my 1/1 car I used to switch off all the garage lights, use one hand-held spotlight and wet the body with soapy water - this forms a smooth film and stays wet longer so you can see any unwanted waves etc when moving the light source - worked really well as my painter didn't have to do any body prep at all! I was hoping to do this method on the model but if I even gently wet the surface the balsa edges expand and stand slightly proud of the surface. Hopefully, once I'm done and the balsa edges are cut out I'll have a uniform filler surface to work with again so I'll then be able to try it.
In the meantime though I will try the household foil idea out - many thanks for it!
John