Here's Mark, W7HPW, taking a quick water break. Mark's help throughout this process was invaluable. I could not have done this project without his advice and help.
Base is 1/2" plate steel. Grade 55 bolts were custom made by Double D bolt in Orem and measure 1" x 27". Specs call for at least 2" SQUARE x 5/8" plate washers at the bottom but all I could find were 4" square x 5/8". That provides even more anchor into the concrete. We used a big pipe to put about 200 lbs. of torque on the nuts holding on the plate washers.