my bubs engaged whilst in labour!
i had a vbac too- he was my 2nd labour
good luck and plenty of time
btw i was told that i would struggle to have a vbac as bubs was going to be too big
at 37+5, he decided that it was time and came out after a very easy labour with no probs at 8lb!
so yeah he would have been big if i went 40 weeks, but i didnt and my body totally knew what to do at its own time
trust your body and trust your instincts!!
good luck