I don't recall any 4/3 on the X side. There is a 5/2/5/2/5/9 type schedule though... three FO lines like this exist currently. Unsure of how senior they go. 8/6 goes the most senior, but with how few 5/2 lines there are it can be tough to say for sure.

With your flight time and experience I'd assume you'd upgrade quickly. Seniority moves a lot slower on the captain side so it could be a while before you can hold it with confidence.