Hi Mark,
I built mine from the kit so my outer stem is ply. I've never steamed, but I've read that a steam wallpaper stripper attached to a length of drainpipe vented at the other end is the way to go. 20 mins for green oak, I don't know about other species.
I live in Rownhams and sail in Chichester Harbour.
Regards
Graham.
Graham Neil
https://port-na-storm.blogspot.com/