Ed,

   I don't know a lot about the DeltaHawk engine, but I think you may come to regret only putting a 200 hp engine in an ES.  Yes it'll fly, but takeoff, climb and cruise numbers will be significantly lower.  There's a reason the Cont IO-360 powered ES didn't last very long.

   Most flying ES's have between 300 and 350 hp engines and I don't think you'll find any of their owners out there wishing they had that much less power.  It's like the difference between a Cirrus SR-20 and SR-22 - completely different class of performance.  I've heard DeltaHawk is working on a 300 hp engine.  Since you have some time before you'll be buying a power plant for your kit, I'd recommend you wait and see if that one is ready in time and focus on it.  In the meantime, I'd do some homework by contacting anyone with a IO-360 powered ES, asking their thoughts and seeing if you can fly in one.  Then compare that to a 550 powered model.  From my standpoint, there's no comparison.

   My .02,

   Skip Slater

   N540ES