Right timing for joing pre-IPO company will be public soon?

Hey fellow Blind users, I need to consult your advice. I am invited to onsite interview for a pre-IPO company. According to many public news/finance sources, they are expected to go public in September. I might be go onsite (and may be accept their offer, if they extend one) before they are officially puclic but it will be hard to start the job before the bell rings. We are talking for manager/director role. Let's say if I get the job offer and even sign it before the bell rings but start date is after IPO, how that will effect my total comp? YOE: 19 TC: ~500K