I'm not a Calvinist, and I don't believe in OSAS, but why wouldn't I believe in an elect that is predestined?
OSAS is not something to "believe in" so im not sure what you are talking about..
There is the fact that if you are born again, you are always born again.
There is also the eternal reality that God who saved someone through faith in Christ, keeps them saved.
Philippians 1:6
Also, when discussing the "conforming" of the Elect, its to be understood that the elect are "predestined to be conformed" not predestined to be the elect.
The "conforming" is simply the end result of being born again, as all the born again are conformed FINALLY and TOTALLY into the "image of Christ", as that is the final end result of all those who are born again.
The Foreknowledge of God, knows who will be born again and also who will make the choice to die a Christ Rejector, but, He does not CAUSE this....as "foreknowledge" is just the omnipotent ability of God to "know everything about everything" = before it happens.
Only God has this "foreknowledge", tho the Bible has quite a bit of it as Revelation Knowledge, and as End Time Prophesy.
Hyper Calvinists reinvented this ability that God has as a twisted theological doctrine of demons that they teach.
They infect "christian" forums like a cancer, like a spiritual death.
See, they teach that KNOWING Is CAUSING.....and in fact, Knowing is only Knowing.
"Foreknowledge" does not mean to CAUSE......It only means to KNOW before it happens, what is going to happen.