I managed to take time to scan in some A3 drawings. I really need a bigger scammer. It’s on my shopping list! In the meanwhile Elements 2, that’s a very old version of the little brother of Photoshop, does very efficient merges. I have version 8 and a licenced version of Photoshop that was going free (about version 10, I think), but despite being more elaborate to use and probably having lots more features, the new programmes don’t do better merges better than Elements 2, bought about 10 years ago (or even earlier).
I can’t always decide straight away whether to use colours, so some drawings will appear again when I’ve done more work on them. The other problem is which way up to show them. This kind of drawing entails turning the paper round as some patterns need a multi-directional approach, so in the end I just show them the way I think they look best.