Protein skimmer for IM 40

I need help finding a good in tank protein skimmer for my innovative marine 40 gallon tank. I have so far tried two skimmer, the doc 9004, which I would have loved to have used, but it would not fit unfortunately with the way the plumbing works in the center of the tank and currently I'm trying the ghost skimmer. The ghost skimmer is pretty awful at the moment and hasn't even produced any skim after a full two days of running. It is also making this horrible noise. I was thinking about using the doc 9002 skimmer but I want to keep spa and I would probably need two of them and I also don't know if those will fit. Any suggestions.