A few Bessies, plus a "Larry's Clamp" would also do the job. The "Larry's Clamp" is a penumatic clamp used to align panels just before the final clamping pressure is applied. Another option is to combine a straight caul on bottom, along with a curved caul on top. When making cauls, either wax them, or face them with Formica to prevent glue from sticking to them.