No I am not certain. I have been going over emails from the '90s but I haven't found where I learned of Elizabeth's birth date.
There was a Nicholas St. John born to Richard's brother John in 1625 but he died about 10 years later. I can't help wondering if John and Richard were reconciled. I winder if there is a grave for Richard at Liddiard Tregoze.
I freely admit that there is a lot of conjecture in my article but I think it holds together pretty well until someone finds new and conflicting information. I fear that the facts may be lost.