When gluing large panels, you have to keep them from bowing. My solution is to buy aluminum square tubing (I use 1-1⁄2″ for panels up to 3 feet wide) and cut it to length according to the width of panels. Simple wing nuts at the ends of each pair prevent overtightening. Drill holes at one end, then a series of evenly spaced holes along the length, as shown. Substitute threaded rod for the bolts if making very thick panels.
– Daniel Kingsberry