My son has started building his RV-7A. He has the vertical stab done, and is working on the rudder. The instructions strongly suggest you use a "sealant" on the rudder trailing edge to help it stay straight while riveting. He has ordered a tube of the reccommended firewall sealant for this. My question is: Is this necessary, what other types of sealant does/did everyone else use? For those that didn't seal the trailing edge, did you have any trouble keeping the trailing edge straight?