Key limes are relatively quick to fruit (about 3 years, some less) and mostly
true to type from seed. It is reported here in Florida that the thornless
variety is not as fruitful as the thorny one, I can't verify this.
I would offer to send you bud wood but with citrus canker in the State I have
stopped sending any citrus anywhere.
Another good sour citrus is the pink variegated lemon. You might give one of
these a try if you have room.
A note on grafting high: Remember to protect to the graft and above it your
plants are frost sensitive. The higher the graft the more wood must survive any
freeze event. I would like to read more about the thought that this increases
cold hardiness, sounds very interesting.