Ok, guys, I appreciate your suggestions on prop selection. Really. :) A lot of you responded with your favorite recommendations.
What I learned today was on a 13 3/4-pound, 72" Dr.1 even largest recommended size (18-8) doesn't do crap. I'd have hated to try to fly it with some of the smaller suggested sizes. The G-23 had plenty of power, but the big Fokker didn't have enough pull to get out of its own way. The engine was screaming but the plane wasn't going anywhere. Can you say "cavitation"? I'm headed to the hobby shop for a 20-5 or maybe even a 22-4. My first Dr.1 flew nicely at half throttle with a G-38 swinging a 22-6. I believe a draggy plane like this one needs the larger swept diameter/lower pitch for more pull and better efficiency.
I used the recommended 2-cycle oil at 32:1. The engine ran fine on the test stand, but cut out in the air on final approach. It's had 80 oz. through it so far. Any ideas? Dr.1 Driver "There's a Hun in the sun!"