I am going to take two wild guesses..

1) I bet when you fly a Kingcat really slow, then go to full power it does not climb
or pitch up... I bet it goes straight at a constant altitude..
If you change that engine angle I think that would change also... But nothing is as bad as a Roo..

2) Maybe BV did not want the exhaust plume near the elev... This plume changes size
with air speed and power settings, and it creates quite the low pressure. Maybe it had something
to do with that.

Eddie Weeks