Spawn mobs on top of trees

So I have some entities that are larvae and i need them to spawn on top of custom trees, on custom leave blocks. I did custom spawning condition and checked for the block below and the block righ there to be the leaves and then tried doing is air at x y z AND is customleaves block tag x y-1 z true. i changed spawning heightmap to be with leaves, set the custom leaves to be solid. but i couldn't get it going consistently. there were a few good attempts but then after some time they just weren't spawning. i even set weighing to huge amounts. any help is appreciated. using mcreator 2024.3 1.20.1 forge