i was thinking why do you have to measure deflection why not use a set amount of flex and measuer the presuer it takes to get it there, i was thinking this could be done with a small digital fish scale, all you would need is something to hold the shaft and a stop above it with a slot for a line wraped around the shaft hook it up to the scale and lift till it bottoms out. or have a clamp on the shaft and stop with the scale under so it would be adjusted slowly? just some thoughts havnt made one so i cant do any better than try to explain the idea