I just measured the cells in my observation hive. They have a 4.9mm starter strip and are building natural comb withoug foundation. These are Buckfasts that were raised on 5.4mm foundation put in the observation hive with a with a Russian queen. It's hard to be sure with bees still on the comb but I took my best measurments on several places and came up pretty consistently with 5.15mm. (ten cells were 5.15cm). This is a drop of 1.5mm in one generation. I'm begining to think I can get to 4.9 in the next generation. In fact, in 10 days when the brood starts emerging from the 5.15mm cells I could put some 4.9mm foundation in and see if they will draw it.
[This message has been edited by Michael Bush (edited August 18, 2002).]