Your ? is 3-1/2" on mine, your 16-3/16" is 16" on mine. Your 30-7/8" is 31" on mine. Wood is 3/4" thick. The stop block is 3/4" by 3/4" by 4". Most other dimensions on mine would not be reliable. I will post some pics I took this morning later in the day. With your dimensioned photo, I have confidence to build my seat base now.
