Sorry, I just realized I put the post in the wrong section.
I created another one in the correct section.
If you agree I would delete this post to avoid confusion. If you like and want, I invite you to re-enter your considerations in the new post.
Regarding your considerations, I agree with you that things are certainly related.
As you wrote the rate of climb would seem very out of parameter.
For my tests you can assume a DI ~=150 200.
The optimal climb speed is linked to the DI, in this case I calculated that the optimal should be around 0.82. In any case it is irrelevant, as long as the aircraft does not climb with an AoA higher than 6°, it should always be able to reach the optimal altitude.
Best regards, NED
EDIT1: Ignore the first part, a moderator must have helped me.
EDIT2: When I wrote the post I was away from home and I was remembering, the DI for the configuration is ~=200.