Here are two more "invaluable" rubberband tricks.

Strung between pencils or chopsticks they make perfect fuselage clamps. Can be a test of dexterity (hint, do the lower ends first)

If you look close at the horizontal stabilizer you'll see a chopstick under with rubber band over. Use a pair of each to hold the control surfaces in straight alignment when zeroing control rods and servos and for setting 0º or 0" on alighment gauges.