Mark Mandell - Gone Round In New Jersey
I've done it that way as well. Assemble the M&T to mark the tenon. Drill the second hole. Then glue, assemble, and drive in the pin which will pull the joint tight even without the clamp. Did several tables that way because I had trouble properly clamping a 6' assembly of the breadboarded tops. I prefer to use the clamp because I think it takes some of the stress off the sides of the holes.