Let me add $0.02... the real reasons for wing seating tape:

1. If the wing saddle is vulnerable to exhaust oil from the engine, then use seating tape to minimise the amount of oil that goes into the fuselage.
2. If the wing is mounted using elastic bands, there are a whole lot of reasons for cusioning the wing saddle a little bit... BUT, I have found that the most practical reason for the tape is so that you always put the wing on in exactly the same place every time. Put the tape on the WING, not the SADDLE. Measure it up carefully so that the wing is seated exactly in the middle. Add the elastic bands. Let it sit for a few moments. The indentation in the tape now serves as a permanent guide to future wing installation! With dowel/bolt wings, this is never a problem.

gus