Cavity tray/window

[23vc]

If I'm putting a cavity tray in under a window (new build not retro fit) using 450mm DPM, is it ok to have the inner leaf side of the tray sitting on the top of the blocks which form the internal window cill, which will then be plasterboarded over, or does it have to sit 1 course down ie. Bedded between courses? It also extends either side of the window by at least a meter.
Hope I've explained it ok
Cheers

 

[^woody^]

Why is the tray going below a window?

In any case that proposal is OK.

 

[23vc]

Cheers. It's going across the whole wall above a lean to roof abutment . I thought I'd just continue it under the window to be safe