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Just remembered my last experience with severe carb ice was about 50 miles north of you and Paul, flying down the Mississippi river in southern-most Wisconsin the early summer. Overcast at about 3000'. I had a constant speed prop, so rpm was constant. I was enjoying the scenery and I started to notice that I kept loosing altitude a little at a time at cruise. I thought this is strange, so I did a scan and...what the !...manifold pressure was down to about 18". I quick pulled the carb heat on and it almost killed the engine (O-540), so I pushed it back in and eased it out a little at a time. MAP came back to normal over a short time and I left carb heat about half on until my heart beat returned to normal. Checked every so often after that.
Out here in the mountain west, carb ice is about as common as Maine license plates, so you get a little complacent. Mind you, the experience that I mentioned was nearly summer time. OAT was probably in the mid-60's, so it can happen any time the humidity is right and there is enough air going through the carb.
I agree with Sam, that two muffs, each with specific design is the way to go.