if you make up new wire sets of exactly the correct length, you might want to consider using enameled magnet wire. It is lighter than plastic sheathed wire. If you cut and solder them to exactly the correct length and avoid connectors you can save quite a bit. On the small servos you can use 26 or 28 gauge wire or maybe thinner. It is very hard to solder to the circuit board in the servos. The signal lines from the Rx to the GP can be 32 gauge. Remove all the pins from the GP and direct mount the wire. Take the pins out of the Rx and solder short wires of the exact length to the GP.
The insulation on enameled magnet wire is very tough. It is also very high temperature resistant. You can safely twist the wires together and test for shorts. There is very low chance of them shorting.
These guys use them to save weight and to directly power their motors.
http://grenadeindoor.modelisme.com/747.htmIf you can get some of the correct gauge for the ESC to motor connection you can save weight over the plastic sheathed wires. A good source of this wire is electric motor rewind shops. Many gauges are stocked by most of them, usually in big paper or plastic barrels with 1000s of meters in each
Also directly soldering the ESC to the motor certainly saved weight. The connectors and wires are heavy.
Would the aerodynamics be improved by cutting off the "tip tanks" like the FunJet Ultra? Maybe sand them off and make them an extension of the wing to add wing area. As you have the FunJet Ultra you can compare the wing tip shape to see if the Ultra has extra wing area or just tip tanks cut off.
You can hollow out the canopy with a Roto-Tool sanding drum.
Just some ideas. Weight saving is hard and tedious.
What about removing the GoPro case and mounting it in the canopy.
Jim