I built the Senior last year and had two failures with it, both times the horz stab broke. Investigation yielded that the leading edge repeadtly broke which then caused the trailing edge to break and then things got hairy on the controls. I managed to save it both times. I was driving the plane hard which is not what you do with a Senior. The twist in the fuselage is a real problem in my mind. So, I decided to build a new one with the following mods.

1) Bolt on wing.
2) Sheeted bottom of fuse with 1/4" balsa.
3) Sheeted top with 1/4" balsa.
4) Sheeted sides with 3/32 balsa. (entire side front to back.
5) Sheeted horz stab 1.5" LE and 1" TE with 3/32 and cap stripped the rest of the ribs in the stab.
6) Increased rudder size to ease ground handling.
7) Took most of diehdral out of the wing (1 degree, orginal was 4 degrees).
8) Used dual aileron servos.
9) Boxed the main spar.
10) Beefed up landing gear area with another 1/4" ply plate.
11) Put a set of 3/16" gear with a 24" span to make it more robust and easier to land without scraping a wing tip.
12) Sheeted the wing from the center for 3 bays on each side with 3/32.

I did not do the two piece wing but I did reduce the overall size of the wing by deleting one bay on each side. I don't believe you will be able to do a two piece wing on an existing wing that has been glued together. It would be easier to build a new wing than attempt to tear apart the existing wing. Good luck, I'll post some pictures of mine in a couple of weeks when I get done with the covering. Jerry.