Light Proofing Door Ideas

My veg lights are about 4 feet away from my flowering tent. The room is full on lit up. I keep the vent flaps of the tent closed and just have a foot of some round 4 inch flexible ducting going into the tent ports for passive air intake. I situate the ducting on the sides/back of the tent pointing away from the direct light. There should be enough negative pressure from your exhaust to assist pulling the air passively into your tent.

Ok outside the box thinking. It sounds like you can not damage THIS door.
New interior door is $49 and it is your door. Hold the other one until done and reinstall. Prehungs are $69 and its 3 pins and bam.