Portco VP Finance Equity Comp Expectations

Long time lurker here, hoping to tap into your collective wisdom.  I'm specifically looking for guidance from those with specific experience in a similar situation, rather than speculation.

I'm about to receive an offer for a VP Finance role at a ~$150M PE portfolio company.  It's owned by a highly respected sponsor, they're about ~4 years into the investment, and are saying they expect to transact within 2 years (almost definitely more than a year, but less than 3).  

The role is open because the prior person left for a portco CFO gig.  He was in the role for 2 years, and I don't think the role existed before that, so presumably he had only vested ~1/2 of the time-based equity (lots of assumptions here, but still).

The recruiter has said the equity will be "substantial" and it will be the highest equity outside of the C Suite.  Of course "substantial" is meaningless in a vacuum, and "highest equity" could mean on a per-year basis, as I would think that other VPs hired at the beginning of the deal would stand to gain more from the sale.

My question is this: given the transaction time horizon, title, etc, how much equity should one expect in this situation?  Obviously there are rules of thumb, but the additional wrinkle of course is that we're already 4 years into this.

Thank so much!