I would think the answer to your question has a lot to do with the size of the inlets your Arf has. For instance if you have a F15 with big inlets you might do well to have a bigger gap around the engine but if you have small inlets like on a S.M Hawk you might get away with a smaller gap.

This bypass size, tail pipe distance/size Augmenter gap is a bit of a black art. No one really seems to know what's best and manufacturers seem to promote their set-ups on the fact they run cool and not what thrust they loose or gain.


Jason