Opening theme tournament is only casual

I try and create a Sicilian Theme tournament and it will only come up casual-why?

Because there is no way to verify that your custom starting position is balanced and does not distort the rating system.

Is there a way to make sure that custom starting positions are valid?

Simple answer: nope!

But I have a Ruy Lopez custom tournament that is rated. How can I make these custom tournaments rated? Is it trial and error with the starting position?

There is definitely a way to have the best of both worlds-a theme tournament that is rated. Somebody here has to know how to do it.

Rated tournaments from ECO opening positions are surely possible, I also want to know how.

This question's answer is not logical

When lichess creates arenas from a certain position, they choose equal positions. Some openings, even if they have a ECO, are not equal. Thus, lichess is programmed such that all from position tournaments not created by lichess are casual. A solution to this would be to program a list of equal opening positions, and a tournament with the starting position as one of those opening positions could be rated. A thread could be created to discuss certain opening positions and if they should be allowed for rated from position tournaments.

Your statement is not true. I just checked a kings gambit arena and the starting position is evaluated -0.9 far from equal. The problem appears to be pasting FEN from Board Editor. You used to be able to select your opening from a drop down list. Can't somebody give me the real answer why my fen won't do what other arena creators seem to be able to do?