Im just finishing up a batch of Jamils Milk stout and it is phenominal! It calls for a pound of lactose but balances it with a pound of black patent. If you want to give a milk stout a go and don't want to worry about ruining a batch this is a great way to go.
+1 on the one gallon experiment thought. I'm all for small batch experimentation. You could do the milk stout recipe and rack off a liter or two before adding the lactose, add your sweetend condensed milk to this and ferment in a smaller vessel (one or two gallon bucket, or a growler if you keep the sample small enough) Then you can compare it and judge for yourself.
