1. yes, the tree should retain its natural characteristics if it is grafted to a 'random' rootstock; although Zill is apparently doing some work with 'dwarfing' rootstocks, its unlikely that a random rootstock is going to impart any significant characteristics such as much more vigor or much less vigor.

2. Turpentine is the preferred rootstock for commercial grafting for a couple reasons....they generally come true from seed, are relatively nematode resistant, and have historically performed well in Florida's calcerous, high-pH soils where most mangoes in the US are grown. Also, turpentine trees produce very well so there is plenty seed available to grafters.

But the truth is it *usually* doesn't matter if you use a random non-turpentine seedling. So you are probably fine in that regard.

3. Seedlings typically grow pretty rapidly, but it depends on what type of graft you are going to be doing. Technically seedlings can be budded at 2-3 weeks of age, but this requires a degree of skill that most non-professionals don't possess. For a seedling to be veneer or cleft grafted (the 2 preferred methods for hobbyists) you would likely want to wait until the stem is at least pencil-width thick, so perhaps anywhere from 6 months to a year depending on how fast the seed is growing.

Good luck!

Thanks a bunch! I'll give it my best shot. :)