Maybe this can help you ;)
https://moi3d.com/4.0/docs/moi_command_reference8.htm#flow

https://vimeo.com/370146519

or go there https://moiscript.weebly.com/trucs-astuces.html (on the middle of the page)
near this!


if you don't want register to vimeo

And you are not obliged to take a surface!
A straight line and a curve are sufficient!
Not at the good place, size etc ... just for the concept! ;)

PS seems your object is not a solid ?