Bi fold door flush threshold damp course issue

[HammerTime]

Hi, I am fitting bi fold doors between my conservatory and house. I am aware that it needs to be external grade to cover building regs for insulation which it is. I have lower threshold cill on the door but as it is its not flush!

My question is can i cut below the damp course to lower cill so it is flush? Obviously I would re lay a damp course lower down under the cill.