Back in the days when ICDF was popular it was generally refered that BVM power set ups only worked fine in his own designed models. And it was generally acepted that it was very hard and difficult to adapt it to other model jets, so be prepared to test and test againg till you get your desired results.

Regarding your last comment I agree that all ICDF models I owned had the wedge going to tha fanīs face and having a hole for the spinner thus it may well be a problem with your model, but I also notice something that takes my attention: the fan is very far away from the model air intakes. The BVM models I had and others I know have the fan far more close to the air intakes and, in fact, I only remember a R/C model Grippen with a Ramtec unit and OS .91 from Mr. Paul Gray to have the fan nearly so back in the fuselage.

Hope experts put you in the correct way and get the performance to get that beauty Mirage 3 in the air.

Best Regards.