Gary Wooding’s device (MEW 319) was very similar, if not a copy, of Jaques Maurel’s tension meter.
The original EIM article was published in June 2016
If you PM me, with an E mail address, I can forward copies of the original article, and a letter from Jacques about the device, showing the calculations.
From memory, for the “normal” 1/2 x 0.020″ 4 1/2″ bandsaw blade, the correct extension is about 0.05 – 0.07 mm. Since making and using the device, I need to change blades so ararely that I have either to rely on memory, or to look up the calculation.
Howard