Put one on my Boss a month or so ago and can't believe FRPP didn't include one from the factory. Not even two weeks later I emptied two tablespoons.
Wow. There must be some major blow-by on that car. I've got passanger and driver side JLT catch cans, and after running at the track multiple days, and going for 250+ mile trips, through lots of twisties and playing with Porsche's, I get absolutely nothing in my driver side can, and maybe a couple drops in my passanger, but still not even enough to dump back into my valve cover. I'm an 07 GT500 @18lbs. These catch cans are awesome, and look great, but I'm still waiting to see the oil!
Regardless of how much oil ends up in this catch can, it appears to be a well-constructed piece and at least the vendor is on here so you know they've got you covered.