its actually just a little larger that the atb 840. by like a half inch, and just a little smaller than the K2. THe neck is 4 inches as well. So its actually pretty well balanced. I cant say about the new pump as I havent gotten it yet. But its running a sicce right now. For its price I think it will be a hard skimmer to beat. I ll have to talk to the builder as I am running mine at 7 inches of water. I am not sure what he designed it to run it at for sure. I ll play around withe new pump when it comes in. I can say I have been running it now for a couple weeks.