Danny, I ended up putting my AquaticLife skimmer in chamber 2 next to and to the left of my InTank basket whose water guide hooks onto the side wall separating chamber 2 from chamber 1, and just had some rubble and a little floss in chamber one. I didn't use an ATO cause tank lid kept my evaporation rate very low. BTW, you can disconnect the fan if it is too noisy - I called BioCube and found out this is an acceptable solution.
First, I cut a 2.5" piece of pvc (think it was that size) several inches high (don't have anymore or I would measure it for you) and then drilled it out to look like swiss cheese. I threaded the power cord through one side and so the skimmer sat on it just fine. Worked pretty well except it did collect some detritus because of size and I couldn't adjust it up or down. Then, I bought the Octo Magnets, only ones I could find that are fully coated, and just put one inside the skimmer which was still in chamber 2, and the other on the back of the cube to hold the skimmer in place. Worked great and if I needed to tweak the skimmer some for height, it was very easy to adjust.
Like you, I searched and searched for a solution and read different things about how easy or hard the Tunze was to fit in; I ultimately concluded that I would have to modify the tank for it to fit and since the tank was full of fish and coral I didn't want to do that. Plus, I found that the AL worked great once adjusted; just rinse it in water and vinegar to remove the factory oils and be a little patient with it. I did add the air tubing modification you can find on YouTube to quiet it down and it worked well.
Good luck, I have since sold this tank but remember enough to write what I did if you need more detail.
