ORIGINAL: Brenner
A few more thoughts: (warning! not all of these have been tried. At least not by me ...)
A PGP F3A Lightwall 30mm wing tube to replace the EPS filled tube that comes with the plane. (~ 1 oz)
Corrugated Nomex servo tray (use the fibreglass skinned version if you use a 2.4 Ghz RX)
Carbon Fiber Spinner from NetBox Hobby (~ 3/4 oz)
Shorter Bolts (~ 1 gram)
Custom fitted servo extensions that don't have any excess length
Bolly Carbon Fiber Gear, and Wheel Pants (~ 1oz)
Titanium pushrods for ailerons and elevators
Eliminating the receiver switch, and just plugging in the connectors when you want to fly (~ 1 oz)
Dubro Plastic Clevices with Brass Pins
300 mah Li-poly RX battery with regulator (~ 1oz)
A high voltage BEC to replace the RX battery entirely (~ 2 oz)
Half Height Servos for Ailerons (~ 1oz)
Use a 21 X 14 APC prop instead of a 22 X 12 APC prop (~ 1oz) (for Electric Version)
No internal ducting (for Electric Version)
MK plastic Tailwheel
A 4350 mah 25C battery (for Electric Version)
Shorter Wing Tube
Shorter Stab Tube
At the nats I thought I was close on weight ( my scales were off cause I was well withing 5000g on the Nats scale) and I changed from an APC prop to a Raza Carbon fiber (thanks Chad). The savings was 28 grams and I'm convinced that the CF props work a little better.
We also reduced the weight by building a custom cut foam and balsa wing on them. Weight savings is 6 to 8 oz's.
I have seen some guys save weight on the long servo extensions to the dual elevator servos. They only use one + and - instead of both. Saves a little.
Light weight vinyl is also a way to save weight vs. a painted plane. Mike Mueller