Miloh, thanks for the response on motors for the Extra 300. I have not ordered the airplane yet and am trying to establish if a .75 something will fit horizontally under the cowl with a pitts muffler. I am not planning to do 3-d with this setup, just some spirited pattern stuff. I have been running a Tower.75 with a Bisson pitts combo in my GP Shoestring which comes in at 8# dry with a 26 oz wing loading. Moves it along pretty well at about 80-90 mph, doesn't have unlimited vertical, but is propped more for speed. (The tower .75 puts out 2.2 hp per their specs.) I am thinking of this combo, the ST.75 or a Fox Eagle .74 if I can find a pitts muffler to mate up. The Tower and Fox heads are round and smaller than the ST heads and may fit in. Anyway, I would still like to establish if the ST.75 will fit horizontally in the 66 inch 300, as I have yet to own a ST. and would like to try one out. Will wait on the engine decision until you get your plane and see if the ST.75 will fit. Others may be interested also,so it might be a good exercise. Am also going to contact VF to see if they know of anyone who has tried fitting a .75 and will post how it worked out. Thanks, Joe