<<The question I am raising is if someone were to market an engine that actually produced an honest 270 HP up to higher altitudes, would it be accepted? More importantly and personally, would you buy it?>>

Just an answer. In the case of my IV-P, NO! Not at any price, not even if it was free.

The reason is takeoff performance. My TIO 540 makes 380 Hp on takeoff. Limiting it to 270 Hp would be like having a 10,000 foot density altitude at sea level without the benefit of the turbos. This same engine makes 339 Hp at FL280.

Now for the real question, can I get TWO of them under the cowling?

Regards
Brent Regan