Lycheeonline.com has a wealth of information for lychee. I purchased a sweetheart 15gallon that was about 5ft tall and had a canopy of about 3ft. The stump was about 2inches. It has been in ground for a lil over a year. Currently right now the canopy is about 4ft and the stump is a lil under 4inches. I have about 14 panicles with fruit the size of a dime and biggest one the size of a quarter. It has already started aborting anything smaller then that pea size.
I think a lot of my success is due to what I did right from the start. I picked a location that had lots of sun 8hrs plus! and nothing shaded the tree. Because of this the tree doesn't have wind protection so during the fall I would set up wind screen. Unfortunatley, this year we had a lot of windy days I did lost a couple of branches. I have heard branches or trees that are shaded will not bare fruit.
Then there is fertilizing. If right now you have no fruit apply micro nutrients, week after apply iron, and finally balanced fertilizer. I always use half doses. It is better to under fertilize. I use a mixture of organic and oscomete slow release. During late fall I would do another round of micro nutrients and iron if needed. Also I withhold nitrogen but give it P and k. I use kmag and bonemeal. When flowers are expressed I would do half dose of balance fertilizer and do this again when fruit is pea size. Think the tricky part about fertilizing lychees is withholding the nitrogen. Remember organic fertilizers last a long time so keep that in mind. I am still trying to refine my schedule. This schedule made sense to me because it matches when the tree needs for nutrition. Even if I don't get fruit I see success in the size of my tree vs. my neighbors which bought it the same time I did.
From what I heard pruning plays a big part too it supposedly set the clock for your lychee tree. You want your lychee trees to bloom as early as possible in the winter. The ones that expressed first had the most fruit set and currently have the largest fruits right now. I pruned mine at the end of june last year. This year if I have fruit I will of course prune all the branches after fruit has ripen.
Finally I make sure the tree gets water once a week in the fall and winter. Of course if it rains I don't water. After flowers are fully expressed I do once every 3 days. If it's hot every 2days. Mine gets about 8gallon per watering. There was a day weather channel said it was going to rain and I let go on for 4days. I don't know if it's just conicedence but a handful of good size fruits dropped.
I know it's a long read and I hope it helps. There is a wealth of information I got from this site so this is my lil way of paying it forward. Good luck hmmm can't find a way to insert pictures