Thanks to @Brian55 for posting this link to Tim Vandergrift's update on his Extended Maceration experiment:
http://www.bing.com/videos/search?q...DF3F983460B118180E80DF3F983460B1181&FORM=VIRE
On Tuesday I started Extended Maceration on a CC Showcase Amarone in my Fermonster. I used BM4X4 instead of the kit EC-1118 yeast. I put the skins in the bag once again. This time I added water to bring it to the full 23L mark. I checked on it this morning...... Overflow! I used the Fermonster lid with the opening for a bung but just hung a clean old T shirt over it to keep the bugs out. This morning the shirt was soaked in juice and I had about another half cup of juice leaked all over. In some areas there was spray as though it came out under pressure, which I'm sure it did. It was the most pleasant smelling clean up I've ever done, but it was a mess.
I did not stir it yesterday, perhaps if I had I could have released some of the building up CO2 more gently and avoided the blowout. Maybe it would have just volcanoed on me then. I sure was hoping that keeping the skins in the bag was a key to avoiding overflow. Seems as though it isn't.
I ordered a second Fermonster that will be here tomorrow and I'll start another EM on a CC Showcase Old Vine Zin on Saturday. For this one I will go back to leaving the water about a half gallon short and see if that buys me enough room to avoid the overflow.