Hydro Junkie

Building light is something that has to be learned, not something that is intuitive.
As B2B stated, for example, there are ways to take weight out of the tail feathers in most trainer aircraft:
1) Stick framing, as he mentioned, is one. While not difficult, it's something that a new builder wouldn't just do since they wouldn't have a clue as to where to start.
2) Lighter materials is another, but this is one that must be learned over time since too light can be as bad, if not worse, than heavy. A mentor would be invaluable in this case.
3) Cutting lightening holes in the solid structure, again, something that must be learned since too big or too many will compromise strength. This is another place where a mentor would be an asset

For the experienced builder, all of these are "no brainers". For the beginner, they are things that wouldn't even be thought of or considered. If you compare the Sig Kadet MKII and Seniorita, the Seniorita has been lightened by changing the slab sides and tail surfaces in the MKII for a stick built versions. This reduces the weight but, for a beginner, it increases the complexity by a factor of three.