Sorry William, I completely missed your earlier question. Yes, I personally feel that approach graft or innarching is the best way to create a multigraft Lychee tree. I would not worry too much about chromosome incompatibility because it appears that the grafts by some of the more experienced Lychee grafters like Max shows that so far at least, there are no incompatibility issues. I urge everyone to try so that we can gather more data.
Yes, Lychee seedlings grow very slowly but the seedlings with a tap root for some strange reason seem to be more adaptable to adverse conditions once they get past about the 2-5 true leaf stage. This is similar to Mango(most are seedlings)
http://tropicalfruitforum.com/index.php?topic=1835.0http://tropicalfruitforum.com/index.php?topic=21350.0and Avocado
http://tropicalfruitforum.com/index.php?topic=12844.0 Not sure exactly why and I don't have any scientific data but anecdotal evidence and reports seem to show that seedling trees do really well and grow extremely large and fruitful. Maybe it's because they don't have to expend as much energy on producing flowers and fruit and can thus use these additional resources to ward off diseases and spread its tap root far enough to find whatever nutrient it needs more of.
Lychee can be grafted young and I'm starting to find out that many if not most fruit species are highly susceptible to grafting at the epicotyl stage when the plant tissues are not fully differentiated. Once the epicotyl leaves are gone, young seedlings are still very open to grafting when their trunks are in the green wood stage. It is in the brown wood stage where grafting becomes more difficult and a grafted usually moves up the canopy to find younger green wood to graft.
By keeping careful records of your trees and neighboring trees, you can track when your tree is in an active stage of growth where cleft and other non approach type grafting may be successful. This is extremely important because we can often get scion material shipped to us but they are lacking roots.
In this experiment here, I was somewhat successful with approach grafting a very young Lychee untill an animal knocked over the pots and severed the connection.
http://tropicalfruitforum.com/index.php?topic=17204.0Simon