Hello there, we allready have this kind of topic:
http://www.oddworldforums.net/showthread.php?t=10017
It's the first one of the "General Oddworld Discussion"
Anyway here are the answers:
1)a) To see what's under a big bro slig's mask head over here:
http://www.oddworlduniverse.com/togg...O/CAMO0001.jpg
http://www.oddworlduniverse.com/togg...O/CAMO0002.jpg
http://www.oddworlduniverse.com/togg...O/CAMO0003.jpg
b) Slig have to wear them because Glukkons things they are ugly without it.
Lots of speculation also say it's for commanding their pants or help them breath.
2) We have no idea. All I can say is that they pack to capture Elums, so I'd say they are about the same size.