Roof ventilation tiles - where to locate

Hi

I'm looking to install an in-line ventilation fan in the loft space to ventilate the bathroom. Running the duct out of the soffit is out of the question as it'll cause a variety of problems, so I'll looking to get a roofer in to fit a ventilation tile.

Where's the optimal location to fit the tile? I reckon that having it just above the insulation is the most practical (with the fan installed slightly higher so that it's on an incline, with rigid insulated PVC piping between the fan and the vent) for ease of access, however I've heard a couple of other opinions such as it should be fitted on the lowest course, or it should be fitted on the 4th course.

Which of these makes the most sense to you, and are there any other options I should consider?

I could of course just ask the roofer for his take, but I'd like to crowd-source this and get as much info as possible!

Ta

 

Thanks - I have already mentioned that it'll have rigid insulated piping. Don't want to fix one problem only to have a new one pop up! The fan will be mounted higher than the vent itself, so gravity-assisted expulsion of the condensate won't be a problem. I'll get it mounted as low as possible.