I clamped straightedges to the gear legs (i.e. checked alignment of gear legs). Measured distance between the straightedges on both sides and relative to centerline and calculated the angle. The formula is based on a right triangle (formula is sin-1 O/H - O iso opposite, H is hypotenuse) - or see here to solve for the angle (https://www.pagetutor.com/trigcalc/trig.html)
In my case, the measured angle came out around .15 degrees which is within the range of acceptable. I'm 46 hours in so far and all seems well.