I'm not trying to talk you into anything here.

Think it over before you attempt anything.

Cut the wing tip off one and a half bays in from the tip of the wing .... in the middle half way between the ribs.

Take the tip piece of the wing, pin it to the bench.
Now butt all the pieces that you need to build the extra bays together, to the tip that is pinned to the bench and build the extra 2 bays.

Epoxy a length of dowel rod that is one bay wide to the back of the end of the dowel that will be re-attaching to the wing.

Do this to all pieces that you cut off the end of the wing. Not with dowel rods but with pieces like the ones you used to build up the extra bays.

Butt the new end pieces that you have created against the wing that it was cut from.
Pin the wing flat against the new piece and epoxy the dowel rods together and zap the other extended pieces together.

It should be straight and even stronger than the rest of the wing.

It took me longer to write this than it takes to do it.
Ron