In order to assemble the control pieces accurately, I made a jig.  Using 1" square tubing, I drilled 3/16" holes 4-7/8" off the table.  This is the measurement given in the plans plus 1/2 diameter of the 1-1/8" tube plus .058, the thickness of the bearings.  The holes are exactly 18" on center.  I will use this same jig to weld the control stick brackets to the 1-1/8" tube, but will have to drill the holes out to 1/4" inch.   I cut the .100 thick control link ends with a plasma cutter, clamped to a grinding template, and final shaped with an abrasive cutoff wheel and 12" disc sander.
I matched drilled the two 3/16" holes in the link ends. Cutting the bushings with a die grinder and abrasive cutoff wheel
Bushings sanded to length and deburred Link bolted to the jig
Welded and completed link