How do I extrude an angle along a curved surface?

[Adn_Kocc]

Try _Flow along curve

Flow along curve and boolean difference together

Hi, I use Rhino for Jewellery Design mostly. When I place stones or other shapes along curve (there might not be perfect round ring) they always get distorted. And even if I use , for example in a round ring, polar array and then I use bollean difference to cut the holes to set the stones the holes get distorted. Is there a way to resolve this? Thanks! Joana