I haven't done it, but in that situation a technique that might be worth trying is to attach 1/4" bungees tightly from gunwale to gunwale just on the upside of each station and have enough tension to hold the stringers in place against the station as well as being able to quickly readjust them to one's liking. If a temporary pin is placed in the keel stringer a corresponding distance on the downside of each station, the stretched bungee will show where to carve off each station with that particular spacing. I would use as many stringers as necessary to make the shape/lineout wished.

The idea is to be able to readily slide stringers around as well as check future skin/station/frame clearance.

To keep this approach quick and simple, one may need to have a few extra stringers packed tightly against the gunwale or keel (ie already under the bungees) in case multiple scenarios wish to be visualized.

an idea anyway.