I mainly use them for whole hops, because they absorb so much wort. After the boil, I kind of twist the bag up and squeeze out as much wort as I can with my spoon (not bare hands). I have thrown pellets in there too, and haven't seen problems. BUT, I've never used 6-8 oz of pellets so I can't say for sure. They're nice though.
Another option would be to just throw the hops in, and then at the end, sanitize a strainer bag and line your brewing bucket with it (they bags have elastic at the top to hold onto the top of your bucket). If you dump your wort through the bag, it will filter out virtually all of the hops and break material - very convenient as long as you can be sure it's sanitized. Pull out the bag slowly and carefully, and you have a bag full of schmoo and a bucket full of clear wort!