I didn't think of that. What should I use ? Won't the plastic ends cover the holes ?
The plastic will cover them but won't make an airtight seal, which is what you want for the cab to function at it's best.
+1, the corner covers will not make the needed airtight seal. I used toothpicks, broke them so they wouldn't be longer than needed, and added some glue to them to keep them in place. In my case the holes were small enough that one round toothpick did the job nicely.