From what I've built in the past (as well as what I've read), the density of balsa is usually responsible for making a plane light or heavy. I'm sure alot of us have replaced some wood parts that came with a kit due to poor quality either in the form of warpage, too light or too heavy. I know I have! Often times, prior to gluing parts together some of the light ply formers and fuselage doublers can be lightened by way of removing some wood in low stress areas. When building, about halfway through I step back and take a general over-all view of the airframe and try to look for areas where I can save some weight. For example, on a recently built Pica Jungmeister, before covering I got out my 3/4" hole saw and cut lightening holes in the aft portion of the fuselage crutch and also between the riblets on the tail surfaces. Interesting to pickup all the saved balsa donuts (from the lightening process) and see how much weight was actually removed. Prior planning and well thought-out installation of the radio gear is essential by way of having to add little or no nose/tail weight to attain proper CG balance. You might try using Elmer's Pro Bond for areas that may require epoxy but isn't overly necessary like doublers and fillets. Just a little Pro Bond expands (foams) as it cures (overnight) which surrounds and penetrates the joint and then hardens to a sandable consistancy.

You asked for some alternate options - those are some that I use! I'm sure there's others.

Ted