Would this be able to be taken on as a personal item?

I have this small suitcase and I was wondering if I might be able to have it as a personal item on an upcoming flight of mine that doesn't allow carry-on bags (Blue Basic). It'd be the only thing I'd have apart from my checked bag, but according to the product page, it's 19.25" long, which is technically 1.25" past the 18" limit JetBlue has for personal items according to their website (the other two dimensions are within the limits on JetBlue's site). Would it matter that it's 1.25" over? In a sense like, would an employee and/or flight attendant stop me and say I can't take it on as my personal item because it's too big? Or would it be all right as long as it fits under my seat during the flight?