RE: Flaps
I wouldn't consider landing my warbirds without full flaps. Depending on the particular manufacturer, they can be very effective in allowing you to maintain steady, stable control of the plane at (final approach) speeds slower than you could fly without flaps. This makes landings much easier for the pilot AND less stressful on the airframe.
If you'll tell me what you mean by "thrust factor", I'll try to answer that too.
Mike