Excellent discussion. Having read most of this forum with great interest, and being something of a fan of the VP-2, i would like to make a couple of suggestions. First; THRUST and power are both important to the performance of this rather marginal airplane, especially with two up, and given the ‘draggy’ nature of the open cockpit. Thrust is realized by increasing the propeller swept disk area, and this comes from increased propeller diameter. Diameter can only really be increased by decreasing propeller RPM, which implies a reduction gear of some kind. With so many PSRU’s out there, and so much impassioned writing about them i would not presume to recommend, BUT, piston engines produce their power in distinct pulses, and propellers do not rotate smoothly either (turbulence, interference flow etc) so some form of rotational or torque compliance must be built in. Some argue that a belt does this, others add a sprung belt tensioner, some add circumferential springs (like a car clutch plate), but all should be matched to the engines pulse’s at designed RPM, and the number and orientation of the propeller blades. All this to say a PSRU on your VW of choice would add significantly to performance, if not adding actual speed. Be aware that this would raise the thrust line of the propeller, and possibly need a taller MLG leg, changing the static stance of the wing/fuselage, a T/O issue. Second; i would suggest adding the roll over bar, still steel tube, to the BH behind the cockpit seats, not over the front BH. Its effect would be much the same, and it would not interfere with the compass. Were you to add <>50% perforated screening between it and the rear fuselage, you might reduce drafts in much the same way as modern convertibles. See Audi and BMW 4 seat convertibles for ideas. My own VP-2 would have a raised rear fairing, and a radial engine cowling over a PSRU to give a Kinner Sportster look or fairing line.