Can I risk it?

I have a hard shell case, correct height and length but the width is 2cm over.

We have priority boarding from Manchester at 7:40am on a Tuesday mid-september. The flight has about 9 free selection seats left with almost all the extra leg room/front paid for seats still free, so it's rather booked but not full.

I have seen some people saying that early, off-season flights are less risky for baggage checks, but hardshell cases are far riskier. This subreddit obviously shows there has been an extreme baggage crackdown this year.

How likely am I to get away with not being asked to check? I am trying to assess the risk factors in not buying the check-in bag, versus just doing it. Obviously no one flies with budget airlines with the goal of just paying for add-ons.