I had a similar issue. The "legs" that hold the False bottom up, I cut them down as short as I could to eliminate the space under the False bottom. On my set up I had to make a dip tube setup because it moved the False bottom below my side valve.
In short the best solution is to eliminate...
KurtB why does it take so long to to carbonate your kegs?
On that same topic why don't any of the charts indicate the time it takes at the indicated temps and pressures for a 5 gallons of beer?
I have been around welding industry and gas companies for about ten years now and there have been several instances that a CO2, Argon, Helium, or Nitrogen tank has been filled with the wrong gas.
I did something simmilar with an 8 gallon plastic fermantor, I used about 5-6 ft of 3/8" copper tubbing made into a coil, connected to a pond pump in a small tote cooled ( big enough for two frozen one gallon water jugs). The cooler just had distilled water in it. The ambient room temp was high...