How much eaves kick up is too much?

[Digmixfill]

I've managed to get all of the eaves and rafters to play nice with each other. The plane of the battens either meets the edge of the brickwork, or steps in a little. This would work OK for the eaves and first course of plain tiles. A bit late in the game I thought to try and squeeze in an over fascia vent. The vent itself is 25mm tall and if it's fixed to a 19mm batten it creates quite a kick up.  I haven't come up with a way to secure the vent to the brickwork without the timber. The gap in the image caused by the kick up looks huge - it's probably 12-15mm.

 

How much kick up is too much?