There was a lot of friction in the pitch motion of the control sticks after mounting the WD-610 control column to the F-633R and L. I found out (by trying it and then researching on vansairforce.com) that any side load on the bearings causes friction so it is critical to use the correct thickness of spacers. After several attempts, determined a good way to get this right was to install the WD-610 with bolts loose and a best guess at spacer washers. Then remove all the washers at one end of the control column and use a feeler gauge to determine the exact spacer needed on one side of the bearing. I had AN960-10 and AN960-10L washers I had purchased over the years and the thicknesses varied. So I could try a bunch of different washers and measure the total stack with calipers until I had what I needed. Then I would install those on one side of the bearing and then repeat for the other side of the bearing. After completing one end of the control column I repeated the process on the other end. I added this information to the maintenance manual. Installed the WD-611 and WD-612 control sticks. Set the F-665 length after installing the rod ends. Installed the assembly. Realized I need to remove the co-pilot side components and drill a hole through the base and extension to secure the extension. I'm considering alternate methods to the one recommended by SB 07-2-6.