Superb drawing Chas.
You know, I often paint aircraft also and have found one major challenge in it- that is painting aircraft in flight. The dark-mid-light values depicting the shapes can often lead to boring compositions with the aircraft (dark value) suspended in a mass of light or mid value (sky). Like a fly in a bowl of soup. It's a common issue I've dealt with that has made my brilliant drawing efforts result in a mediocre finished work. I see this as a common issue with flying aircraft paintings IMO.
One could introduce an interesting horizon or skyline of the same value as the aircraft and at some point touch the aircraft. Or integrate weather/cloud elements into the picture that do the same but the trick is to do this without distracting from your main character, the airplane.
I mention this as a consideration because it's a great drawing. Your challenge won't be getting the B24 looking right. It will be making the composition look interesting by how you integrate the ground and sky into this.
Below is a DHC-3 Otter, 11x14 oil on panel (I posted this a while back) I like doing these portraits with the wings running off the page because I find the comps pleasing. A pattern I follow often.
Looking forward to seeing yours unfold.