Advise with venting roof when installing Velux window

I'm putting together drawings in order to get a building warrant for my loft conversion.
I've had Building Control come back to me with queries over venting my roof at the Velux windows. The design allows a 50mm air gap from ridge to eaves but the problem comes at the Velux where the trimmers are installed so there is a small section at the top of the window and bottom where there isn't full air flow. Has anyone got any suggestions to overcome this problem? I was thinking of drilling the rafter adjacent to the trimmer to allow air flow but I'm not sure if this is feasible.
Thanks