Greetings
        I have used the plastic foundation since they first came out
about 20 years ago. I never really liked the one piece plastic
frame/fdn combination because the top bar cracks so easily. Also they
are ugly. Where I work now (Dyce Lab) we have a large number of wood
frames with plastic fdn.
        We use grooved bottom bars and the plastic sheets seem to fit
correctly. However there is a serious problem with simply snapping
the sheet into the top and bottom groove. If the frame contains 5 or
6 pounds of honey, all of this weight rests on the bottom bar, which
was not designed for this. I have seen the bottom bars blow out when
handled roughly (like when you thump a super full of honey down on
the truck bed).
        Normally a piece of foundation is fastened securely to the
side bars and even the top bar, if you use frames with the nail in
strip in the top bar. Obviously the top bar and the sides handle the
weight of the honey, the bottom bar simply completes the frame. Also,
if you skimp on the nails in the bottom bar, the weight of the comb
may push the bottom bar out.
        All of this goes to show that there has to be some kind of a
clip to hold the plastic onto the side bar of the frame.

        As far as drawing out plastic, I don't know if anyone
mentioned the fact that you need a great honey flow and a strong hive
to get any foundation drawn out successfully. Under these
circumstances, you can get combs drawn using just about any type of
"starter", even frames with no foundation. If the flow or hive are
not strong, good results will not be obtained. You'll get half
finished combs, and the bees may even chew and mutilate wax
foundations.
        I think the best way to get new combs drawn is to put three
new frames in the middle of a box of used combs. If you alternate the
new and old combs, the bees will usually fatten the old ones
excessively and skimp on the new. More uniform results come from
putting the new ones together in a group.
        If you don't have many old combs, you should at least try to
put a few in the middle of the box. This will act as a magnet to get
the bees working in the box. Once the work is fairly well started,
you can move the old combs to the outside and get the bees to finish
the new combs in the middle, where the energy is more concentrated.

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pb