uses "closed cell foam" weather stripping sort of like what the big box stores sell for around window AC units. Very "spongy" so can compress for the tight spots but fill the gaps.
Can be purchased or ordered pretty thick, local hardware store has it in stock at 7/16 of an inch (11 mm). I think stock on scamp
is 1/2 inch (13 mm) with maybe 3/4 inch (19 mm) on bottom edge
Page is for one size and lists some others further down.
It's on my to-do list also, noticed the light
coming from around lower part of door on camping trip.