Alter things just a little and you can reduce weight. (some...) Sand the surfaces to be glued, and use medium CA to replace almost all of the contact cement. CA is far lighter than contact cement, and will rip the coro before it lets go.

The window shapes glued onto the fuselage side are decorative, not structural.

An alternative... visit www.spadtothebone.com Look at the Debonair. (in the SPAD Originals designs list) Not as pretty, but gets the job of a trainer done. Considerably lower wing loading than the Aircores trainer.

The coroplast trainers are TOUGH! They tend to bounce, not break. The SPAD sites' designs are getting very good. (as people find improvements, they get updated.)