[smuzz]

I've been thinking about incidence measurement lately too (having time on my hand ... that's the singular, on purpose).

I've decided I'm going to buy some low-power laser pointers from eBay and make some jigs and mounts for those so that I can attach them to the model and point them at the wall of my shed which will be five metres away. This will give me some distance along the alignments to help improve accuracy - or, as you say, that's the plan