With that much of a drop you should be getting most of the moisture out before it gets to the big tank I would think.
That's the hope. The most expensive part of this were the fittings. Compression fittings suck too.
Part of the reason this ended up like this is that I wanted the big tank's largest fitting to be the output from the tank to the system in the shop. I figure my on-demand need for air is greater than my sustained need for air, so I ended up removing the in-tank check valve at the top and using that point for the exit, and then having new pressure introduced through the side port, which is quite a bit smaller, but still bigger than the original line that ran from the pump to the tank. I probably should put a check-valve between the little tank and the big tank so that if the little tank, the coil, or the tubing/fittings leak then the big tank doesn't leak out the 80 gallons of air at over 150psi, but then I have to buy yet another inline check valve and even more compression fittings.
I'm mildly tempted to get another Moisture Minder automatic purge valve so the little tank has one too, but they're $80 a pop and that's quite a bit of money relative to how much I use my compressor.