Carton 100mm f/13 "MD" OTA Construction - GSO Focuser-to-Main Tube Adapter Test Fit
 

The focuser adapter and shim test fitted on the main tube. (Click to see an enlarged image.)

 
Test fit of the GSO Focuser-to-Main Tube adapter with stainless steel shim proved successful. With the addition of the shim, the adapter fits snugly and is perfectly center in the main tube. Now, since the tube was cut perfectly perpendicular earlier, the adapter will fit perfectly perpendicular to the main tube as well.