What stack height allowance in window/door reveal for blinds?

[oranjeboom]

Before I insulate my door reveal today and then plasterboard, I need to allow some space for the stack height of the roller blind at the top? By 'stack height' I mean:

 

 

In my case though, the blinds will fit in the reveal itself and are likely to be roller blinds (potentially vertical blinds that stack either side of the door). There must be some standard calculation for this? for every 10cm drop allow 5mm of 'stacking'? Will depend on the material (weight) that may influence the size of the blind 'tubey bit' also.

 

In this case the drop will be 2.1m and the doors open outwards.

 

I'll do some phoning round later today but I don;t have much hope in getting much info from some spotty 16yr old.

 

TIA

[oranjeboom]

"Allow for 60mm" was the answer I got for a roller blind. FYI!