Tim, I use Kapton tape for shims, both along the back rim and three tabs along the slide, that will minimize metal to glass contact. Take the lens and place it under monochrome light if you have it or if you don't use an Engery Saver type bulb. You should see interference rings between the two elements. They should appear perfectly round when viewed from looking straight down on the elements. If the rings are off center, then that usually indictates that one of the spacers in thicker then the others. You said that the spacer were tape ? If so then they don't sound like the stock spacers and maybe the wrong thickness. Jaegers is still around under Jaegers Jr. They might know the correct thickness of the spacers. The "right" way to set the spacing is to set the lens up in double pass autocollimation mode and look at the correction in green light, then adjust the spacing for the least amount of spherical abberration.