The side panels for a 24' Jumbo are 26' long. I pre-scarfed the mid and aft sections. Then I added the bow section to the rest of the side panel at the time of bonding the panels to the bottom and the shelf. I used a jack stand to hold up the aft end of the panel while it was fitted and trimmed. (One more technique for a solo builder.)

 

It should be noted that if you are going to extend the bow, then the forward side panel will have to be widened as well. And the jig must be high enough for ground clearance. In this case, the jig is made from 2x10s and sits on 6 inch casters bolted to additional 2x stock.