About weight -- it depends almost entirely on technique.

I use Titebond II for nearly everything and I double-glue nearly every joint... but my planes are always as light as any similar plane in our club, and lighter than most. Neatness translates very nicely into lightness, and that's a lot of the difference. Put glue where you need it, wipe it off where you don't, add fillets to critical joints, but strike them off neatly and you'll remove most of the weight you put on. Then, as the glue dries, notice that it shrinks to about a third of its original volume... its weight is shrinking at the same time -- unlike CA, which loses almost no wieght whle curing.

I'm also interested in the sandability of the different glues. I'm told that of the Titebonds, original is most sandable, II a bit less, and III leadt of them while original isn't water resistant, II is labelled water resistant, and III is recommended for outdoor use, maybe even labeled waterproof.

For comparison, on a friend's recommendation, I tried WeldBond (a very thick white-colored white glue) recently on a very light electric. WeldBond dries clear (very attractive) and sands easier and cleaner than my Titebond II. HOWEVER, WelBond also is formulated thick to stick to non-porous surfaces and to stay put where it's applied -- and it showed virtually no penetration in the little bitty glue joints of my 1/2A-size electric E-2 Taylor Cub nad was too thick to form a neat fillet. (The Cub is built up from 1/8" square sticks.) As a result, a low drop of the nearly-weightless uncovered fuselage resulted in a lot of damage, almost all of it at the site of suface tear-outs at the joints... the glue was plenty strong, but since it didn't penetrate beyond the surface, a little stress simply ripped the surface off the wood and the assembly turned itself back into a kit. I would not recommend Weldbond on any stick-built / warren truss type structure, especially for light structures with small joint surfaces.

So, that's what I know -- somebody please fill us all in on how Titebond, II, and III really compare? Thanks!