I have made this in the past for the same thing ;)
Very more easy without script ;)
(don't refound the english version so here the translation :)

Décocher = disable
Pour une échelle de 100 = For a scale of 1 / 100

Draw a frame of 20 m * 28.7 (if scale is metter in SU) for be sure to have it in A4 format (21 * 29.7cm)

Disable Perspective in Camera view

In top view with A 4 format
Frame is well 20 * 28.7
Square is well 10 cm * 10 cm
Text frame is well 5 cm
Diameter is well 3. 68 cm

So Scale is good 1 /100

Just adapt for your own using ;)