"Diamond has a bit of a history in keeping their numbers down, their aircraft tend to perform better then published."
Perhaps this statement should have the word worse substituted for better.
The DA-42 is the recent example of far poorer than predicted performance that sticks in everybody's mind. 200+ kts predicted and in reality only 155 kts or so. That is not just a few knots, it is an outrageous 25%!!!
The issue was the size of the Thielert engines (and cooling I believe) and I know that all the previously delivered DA-42s will be getting an engine upgrade FOC in the near future which should go some way to getting from their currently sluggish cruise to something more respectable with not much effect on fuel burn. I am pretty sure they will still not get 200 kts though.
Take a look at the back view of the D-jet it has more gaps than seals - their chief aerodynamicist needs to go back to school - and as for the design - definitely Austrian.
Not for me!
SB