Ventilation for head of window reveal

[Martino]

I am installing external wood fibre  insulation between adjustable wooden joists on the external wall. There will then be a membrane, counter battens, horizontal battens, and vertical larch cladding. At the head of window/door reveals, standard advice is to use a flashing to drain any water at base of ventilated space behind cladding (e.g. https://woodcampus.co.uk/wp-content/uploads/2022/07/9DetailOpenings-vert14-1-15.pdf). In my case, the 240 mm deep joists require closing at base at the head of the reveal, and battens are required to take the larch lining of the reveal head. The only way I can think of doing this is summarized in the attached sketch (hope it is understandable). The cavity behind the vertical larch cladding is vented at bottom and top, but the space between battens at the head of the reveal is only vented beneath the flashing. I can't think of any other way of doing this. If anybody has any alternative suggestions, I would love to hear them. Thank you.

Window reveal head.pdf

[Martino]

Just to add: these two posts discuss related details, but don't quite apply to my case, as the windows are not set within deep reveals: