I made a point of trying to do this this morning, and couldn't work out how to place Velcro to hold the door closed without constantly sticking and unsticking it! So, I had a close look at the latch and it appeared to be just a bit too low, meaning that it wasn't creating any lock when closed.
So, I decided to put a little bit of Velcro under the latch to force it up a bit as you closed the door... Bad move, closed the door and it worked so **** well, I couldn't get it open again!
Some 10 mins later, I managed to get the door open and removed the Velcro. So, tis time input it on the bottom of the door phantom part itself and its working a treat. Tight to get open, but there's no way it's coming open in flight. It's just a 3mm x 5mm rectangle of the fluffy Velcro. Perfect.