Velux flashing question

[HammieUK]

I'm just prepping to fit a Velux window in my loft (GPL S06 with an EDP plain tile flashing kit), and I'm trying to work out what the relevance of the 105mm dimension on this step is about...

Unfortunately, because this window is such a tight fit, I can only move it by up to 50mm, so that means there's only a 50% chance I can achieve the 105mm dimension (won't know for certain til I knock a hole in the roof). Would it cause any problems if this dimension was smaller? It must be something to do with the lower flashing piece, but I can't get my head around what it could be.

Thanks for any help.

 

[catlad]

its is for the flashing to fit you can go inside that measurement if the profile of the tile will allow it

 

[datarebal]

With the EDP the relevance is this dimension is making sure you have the correct amount of headlap (flashing to tile) ..
Just do as the instructions say and you cant go wrong.