Will try the round tank first, directions do not mention any foam,
just 2 layers of double stick foam tape for dampening.

Just weighted a bare wing, sans ailerons, receiver, aileron servo and covering
and a ready to go fuselage and it came to 2lbs 12 oz.
By the time I add ailerons , servo, receiver, covering, elastic bands,
control surface hardware,hinge material I can't see making 2lbs 14 oz.

Just weighted my battery pack and it was 1.7 oz (AAA NiMH). A 2/3 AAA might save .5 of any oz.

Now I realize on the first two I went with full lenght bidi hinges on the ailerons
and straping tape hinges would be lighter (man, that bidi is heavy!!!),
I also used strapping tape for the spar wrap instead of bidi on the first two to
try and save weight.

I just don't see saving half a pound from where I'm at .