I didn't heard around about use of 94mm bore, or even common. Also think, that bore over 92mm is nonsense on VW type I and it only produces problems. Simpliest tuning, without need of machining block and heads, is use of 74mm crank and 88mm bore cylinders - it gives 1800cc. Next cubatures in table, but cranks also exist with 76mm.
I think most (not all) VW aero engine builders agree, based on a lot of experience and a lot of off-airport forced landings, that going above 69mm stroke requires that a beefier bearing be used if we are driving the prop from the pulley end of the case. That means more expense to buy the Force One bearing and hub, and it requires machining of the case. Even without that, a 74mm crank will require case clearancing unless special rods are used. And going with a 74mm or 76mm crank will increase piston speeds and stresses compared to the same RPM with a 69mm crank.
The potential advantage of the 74mm stroke 1800cc engine might be greater HP at lower RPM than with a 69mm stroke 1835cc engine. So better prop efficiency from a longer prop. I'd say the jury is still out on that. Also some planes can't use a bigger prop due to clearance issues.
So, lower initial cost, lower complexity, higher HP, and (potentially) better reliability would be the reasons I see for favoring a 69 stroke/92 bore 1835cc engine over a 74 stoke/88 bore 1800 cc engine. I think the comparatively larger number of 1835cc vs 1800cc VW airplane engines indicates there's general agreement on these points. Right? Wrong?
Edited to add: Are appropriate pistons for 74mm stroke widely available? Expensive? From what I recall, the widely available pistons are for either 78-82mm stroke and for 69mm stroke.
