I'd suggest to staple temporary webbing straps to the rear bow. Adjust the height by measuring window curtain and use the split in top at rear bow and measure down to belt line.

Did you check with Mac/ Cartouche?

The Robbins top catalog usually has the bow height listed.

So I got the rear bow height by using the old pads as a guide. I tacked the new top on and made a little adjustments here and there. I had to adjust the window down from the old one about an inch. I got a rear bow height of 16.5” from the top of the tacking strip to the rear edge of the bow channel.

When it came in he had a broken frame arm and had to get that welded up. The second bow did not lay down correctly. The owner believed the frame settled and bowed. We had to enlarge the front arm bolt holes that mounts to the second bow to get it down about 2 inches. I had 36 hours into this thing including making a well, and a boot.

I commonly use the old bow pads to set the rear bow height. They should have gotten back to you with a proper bow height from Electron Top. Tacking the top on and making adjustments is the best thig you can do in the situation you are in.
I am not suprised you had 36 hours in fixing a tweaked top. When top arms break it is usually by force meanig multiple things have been bent and tweaked. Tops do not really "settle and bow" with out some sort of extreme force. The most important thing in a top frame is that everything is square and straight. Sometimes you will never get it to measure properly but it must operate properly with tension on the top.
I do not think 36 hours is an unacceptable number when it comes to fitting a top on a tweaked.

This Mercury 4-Door convertible was completed several years ago. The top was tailor made to fit the car.