Are you using wax coated or plain uncoated plastic foundation?  I have
had the best results with wax coated plastic foundation in wooden
frames.  The bees draw it out just as fast as regular wax foundation.  I
tired uncoated one piece frames, and I found it took the bees longer to
draw it out than normal.  But I know of other beekeepers who have found
no diference between coated and uncoated.

Allen Banks
Honey Road Apiaires
http://www.honeyroad.com