Tension gauge accuracy

[allene]

Let me simplify my question. I measured my forestay tension with a PT2 and it says1800 pounds but a PT3 says 1225 pounds at the same time. I then pull on the forestay with 41 pounds 54 inches off the pivot and calculate 824 pounds of tension. Can I assume one of these is accurate? Is there a better way to measure the tension? I don't want to overstress my wood mast but I want less deflection under sail.

A complete write up of what I did can be found at http://l-36.com/loosaccuracy.php

I have contacted Loos and they say they measured a PT2 and PT3 and got 1300 pounds on both on the same wire. I sent my PT2 to them. They seem very professional and helpful but the fact remains that I used 4 of their gauges and got wildly different results.

What is the most accurate way to measure this?

Allen