Doing some more looking while it rains. What's the maximum size and HP that will fit? To obtain maximum short field performance. Ignore fuel consumption and range right now.
Can the new HD model handle the extra HP?
From Zenith website. Engine maximum weight 440lb. 150-240 HP
I know there are lots of options.
Looking at the IO-580 444 lb 315HP Lycoming IO-580 - Wikipedia, the free encyclopedia
TIO-540 438 lb 400HP 400+hp Lycoming TIO-540 by Sky Dynamics - YouTube
dry weight, slightly more in service.