Great looking trees sackrat! I know what you mean about the huge file sizes. Did you generate the leaves in Arbaro?
I sometimes cheat by using Bryce tree leaves,(I make the trunks invisible)on my Arbaro and POVtree models. Unfortunately I never got to try MECN tree factory before it vanished. I never met a tree-making app that I didn't like,lol. Have you tried Lsystem4? It's a freeware app that has quite a few good tree presets among others. It's actually quite easy to use and has a built in "mutator" that can help you come up with your own custom versions of the presets.