Francisco,
While driving back from work, I unintentionally started thinking about them figs :) , the seedlings too.
They grow so fast partially because the root system is different than that of the cuttings. So, my question would be the following.
If I let the seedling grow until the next spring, uppotting on the way, and than do airlayering somewhere in the middle of the trunk, will the resulting tree be less vigorous ?
It is going to be shorter, obviously, but what else will change?
The lower part I could use for grafting of some weaker varieties, by the spring the trunk will harden for sure and be thick enough to work with it.