Nope there is a drain on the bottom that goes to a condensate pump. So there is very little if any left in the bottom yes the drums take up room but room is no issue hence the drums
I just thought of this, could you use one solenoid to control 2, 3, or 4 sprayers via a manifold? Go slightly larger on the diameter of the port and step down to a smaller opening on the outputs on the manifold, say 1/2' in - 1/8" out.
I have used hydraulic and pneumatic manifolds before and have never seen much of a drop in pressure (depending on what the starting pressure is). I would say that there might be a reduction, but I couldn't see it as more that 1-2 percent, as long as there aren't too many misters/sprayers. If your accumulator has a pressure of say 115 psi, the loss of pressure, from the solenoid through the manifold should be pretty equal to each of the sprayers, if you are only using 3-4.
I have been doing this for a long time now...and have gone thru all of these issues I use 8 misters per 55 gallon pod - 2 solenoids per pod operating 4 misters each I use separate pumps and reservoirs for each solenoid. This is the timer (12 station - I use two timers) So there are never more than 4 misters running per pump at a time even though I have 20 pods but IMO you are kind of wasting your time unless you use misters with at least a 100psi crack pressure this allows for precision 1 second misting with 100% atomizing - otherwise you are really closer to low pressure aero and this is just the beginning, there is soo much more to consider