Happy weekend, Archie.
Yeah it can be done, but then with the quick and fast versions from companies like sweet seeds, dinafem and seedsman. I think
@Sweet Seeds Jay clocked in his Green Poison FV plants at 40-42 days.
But with a uncrossed jamaican 100% sativa? Meh, plants develop early flowering if their microclimate demands it for survival and continuation of the genetics.
That being said you can find some wicked early IBL sativa at altitudes in Africa, Ciskei is legendary for example, likewise there are very early Congolese strains.