I’ll take a look at those books, thanks!
Following your advice I’ll definitely be stepping up my game with sketching. While I was never close to being a sketching god, I had some reasonable skill. Now it’s been about 5 years since I last sketched, so it’s going to be humbling… Last night I had a crack and it looks like I’m back to first year level sketching. All of the higher concepts are gone 
Meanwhile Im doing my best to keep active with other skill sets. I’m currently negotiating a deal with a major RC heli manufacturer who potentially wants to use a canopy design I did on Wednesday night. Fingers crossed!
I’m really hopeful that this will work out, but in the mean time I’ll keep your advice in the front of my mind! Thanks so much for your helpful words.
Joly