Thanks Ron.
I'm in the same boat. I wanted to design my own shape once and as you state, can't go back 20 years when the math would have been a snap.
Found out that the magazine plans also accounted for optimum use of the mica sheets. My table lamps used the plans dimensions but I wanted larger for the floor lamps and just scaled the plans by 15%. Just over the "optimum" when I started cutting the mica (at $50/sheet)