If the width was just a little wider I would have jumped on a 30L. Instead I'm having AA make me one similar but with 20" width instead of 14" on the IM.
Hard to tell, I havent really been messing with it, havent gotten a nice skim yet with it yet but I had it off for a week or so while treating chemiclean. I was pissed off that they don't even have a solution to mounting it in their own tanks. I ended up using my large sized magfloat to prop it up on the bottom and bubble trap foam to push it up against one side of the return chamber, WHICH by the way you have to remove a freaking media basket for because it doesn't fit in the other 2 chambers.
I have a JBJ30 and like. I really like the dimensions of the JBJ. I believe the owner of IM used to be the co-owner of JBJ so they're pretty much the same design.