What kind of distortion do you see in the Kowa at 60x? My recollection is of some barrel distortion at the low magnifications gradually decreasing to approximately zero rectilinear distortion at 60X, but with the expected large amount of angular magnification distortion.
Henry,
I have just checked the TE-11WZ for distortion using your method of viewing a grid pattern through the objective. My impression was of uniform slight pincussion (appearing as barrel) throughout the 25-60x zoom range. I could not quantify it but it was of similar magnitude to the excellent Swarovski 30x W eyepiece.
John