Soren mauritius and kwai mai pink have less cold requirement to stimulate flowering.If you get any nights below 14 or 15c it should be enough to trigger flowering.Many cv's need it to go right down below 10c for a couiple of nights at least for good flowering.Seedlings are not usually recommended as they can take a long time to begin fruiting.
I just got a Mauritius, my first Lychee cultivar. I have another seedling, of unknown variety, which is very small in 1 gallon.
Anyway I really hope, they are low chill. the coldest it ever really gets in Santo Domingo is about 64 Deg. or around 18C and this happens when we get a strong cold from the north, ( the kind that makes Floridians have to use heaters on their plants ).
Anyway plants are small, even the one I brought over, is just now starting to bud to replace the leaves. the transplant made it drop all its leaves.
I wonder if you can stimulate flowering using ice water on them haha