Draft problem

Hi

I can't create a draft, that doesn't affect the size on my part? I've triede almost everything I can think off

The problem is that when I try to create a draft from the feature above my doublecourvated surface, I can't get it drafted without the size is changing along the side. Anyone got any idea of how I can do this ?

In the end, (see picture above), the size is 590mm but in the middle it's 594mm. I have to get this the same size all the way down the side.

I think the problem is that I draft from the top, but I cant figure out how to start the draft from the doublecurvated surface ?

I've attached the part here, and the feature that's the problem is "Boss-Extrude 9" and "Draft 19" and "Draft 21"

Thanks in advance

Christian

SolidworksParts And Features