Yes I have a 40 pin dual CF adapter in one of my A1200's, and it works great with two CF cards, it also works with one of the cards removed. This is a cheap adapter I bought from ebay.
I also bought a 44 pin dual CF adapter, but this resultet in a somewhat weird behaviour in HDToolbox where the partition sizes showed the wrong values when changed (not talking about >2GB range here). I tried this with only one CF card attached, and I have later learned that some of these 44 pin dual adapters requires that two CF cards are attached in order to work.
I guess that it's a bit of hit and miss with these types of adapters, but fortunately they are not that expensive. One thing I always look for when bying CF adapters is the possibility of configuring them as master/slave.
