I think I may be able to get that from my library, I've been amazed what little community libraries can now access electronically. I'll give it a shot. Of course, it will only tell us how the stock B&S engine was tested, not what a modified one (SE-33, etc) can do. 1) I've never seen the source for the 33HP figure for the SE-33 engine, has anyone read it if was gotten by spinning a calibrated test club, or some time on a certified dyno? It might be based on comparison with flight characteristics of an SD-1 that has an engine of verified HP, or maybe just a comparison of the static RPM produced by the SE-33 spinning the same prop as another engine of known output. 2) The info I've seen on the MiniSport pages doesn't indicate if the 33HP is for short periods or continuous. TiPi reported previously that the SD-1 requires approx 30 HP to fly at 94 kts, and the aircraft's cruise speed is 80-90 kts, so presumably the SE-33 can supply at least approx 29-30 HP continuously in the SD-1 (given the cooling airflow in this "clean" airplane and the tractor configuration). TiPi mentioned previously that he thought a fan might be needed for a pusher or a draggier plane. Edited to add: A page posted by the SD-1 dealer in the UK indicates that, with the SE-33 engine, the SD-1 cruises at 94 kts "@75%" The site also shows that the engine burns 1 GPH "@75%." Clearly, there's a conflict in the info that is out there. For what I have in mind, 29-30 HP continuous would be fine (I'd only need about 25 HP in normal climb and cruise, the 30 HP continuous is for unusual cases, but it's got to be there) and if more than that is available for a minute or so (to get off the ground and over the barn,etc), that's a nice plus. I think if somebody needs 33HP continuously to pull a draggy plane around, they might be in for some rough sledding.