Donna,

In my yout' in sunny Californ-i-a, I used to do some stained glass work
(little decorative tchotchkes, and a couple of ugly lamps), and once asked my
friend who made windows why one couldn't just overlay the lead cames over a
single pane of glass (didn't need no thermopane out there).  The answer was
that it would be fake and look cheesy; you don't get the oddball reflections
from 15 little true-divided diamond lights by putting lead cames together on
top of the glass---so it looks fake and cheesy, just like the crappy Andersen
fake-divided light windows look.

And don;t take out your real thermopane, unless the seals have already failed
(which they will) to put in pain-in-the ass leaded glass.

As far as dividing the glass you have, the way to do it is to draw a big X
corner to corner, and then a series of lines parallel to each leg of the X to
further divide it up into diamonds.

Good luck.  Don't do nothin.
Ralph