Lookin real comfy in there.

Exactly 5 inches of head space.  Perfectly sized, ~2in of substrate to form the o2/proton membrane on top of the anode, and more than enough space to setup the cathode.

No.10 was at 303mv 1.08ma at 8am.  It has since dropped to 302.  It was fairly warm last night so the cell temps are a full degree warmer this morning.  No.10 @ 17.5degC and no.9 @ 16.