Contest Balsa: The older the tree, the lighter the balsa. About 20 years or more for top quality contest balsa. Can't remember where I got that information, maybe Riley Wooton at Lonestar Balsa (long gone). I believe balsa is used in the production of windmill turbine blades which are enormous. One blade filled with contest balsa would probably provide hundreds of airplane kits (much better use, too).

I'm not sure I could afford to have Alex build an airplane for me... :-)
Fortunately, I love to build!