naturally generating custom cave vines

so i've made some custom vines that resemble cave vines and weeping vines, the placement and properties work just fine, but i cant get them to actually generate in caves or on my custom huge fungi properly. I thought of making a number of structures of vines of different lengths since natural blocks dont tick. This is the code for a 3-block tall vine, it doesnt generate at all and im stuck. How can i make the feature spawn on the bottom of blocks?

this is what i was hoping for them to look like eventually when all the different vine heights are added: