Very successful today.
I finally got my drill bit set and drilled out a main jet to .039mm(stock is .038mm), and got a very steady 6000RPM top end on the 20x 8 Zinger with no choke and it would idle as low as I wanted (although under 1600RPM it starts to shake more than I like). Best of of all the transition with very smooth. It's amazing what difference .001mm will make. Top end was down a little (100RPM) but the high humidity today might have had something to do with that.
Speaking of high humidity, the past couple of days have been rather rainy so I went to the library and checked out the Model Airplane News back issues. In one of them was a review of the Fuji 34cc 4-stroke. According to their review, it swung the same 20x8 prop as my Briggs 40cc at 5650RPM! So needless to say I am pleased with the performance of this Briggs. Also of interest was that the Fuji was capable of swinging 22 and even 24 inch props. I think a 22x6-10 prop on The Fokker DVII would really pull it around nicely and I am going to order some larger props to see how they perform.

J