You've seen the site standards and are sure it doesn't belong in casual? (I'm just checking because often people have incorrect perceptions about the levels) You say your expectations are "extra-high-free" as long as there aren't any one liners I would say casual would work for you. A paragraph is the minimum.
That being said, I can't see a problem with you making an interest check in Casual even if you keep your RPin free. The levels are to help people find the RP's they will enjoy. Have you also made an interest check in the General Interest check forum as well?Casual Roleplay - Some standards. Roleplay here if you enjoy writing at least a paragraph or two, character development, and some depth. Casual RP is more laid back and lighthearted than Advanced RP but more moderated than Free RP. It's a good middle ground. No one-liners.