Follow what Ken says, but also add some 1/8" sheet cut to size along the each side of the stringer about 1" either side of where you'll do the splices. If you can do a diagonal cut, or scarf joint, on the aft portion you'll have a stronger joint.

Also those longerons are structural. Your landing gear mount plane attaches to the bulkheads these run through. Just a bit of extra material to help strength the area and help transfer the loads out of the area. Before you re-sheet, put a small piece of fiberglass cloth between the landing gear plate and bulkheads. Also use some sheeting as doubler material where the sheeting will join - this will make up for the strength lost with the cut sheeting and butt joint that you'll end up with splicing the new sheeting in, and give a little shelf to help attach the sheeting to.

Hogflyer