Trees as structural Posts

Can anyone offer any advice on using trees as structural feature posts. I live in a tree house as it is but the new build extension will have a couple of 6m posts and four at 4.5m long.

I have a few cut and prepared 12" posts already but finding some this length and condition is proving difficult.

I found some nice straight trees today and seem ideal for me 1700bt a piece and 6.5m long.and 8-10"diam. They still have bark on and in the raw. Cut a month ago.

So if I want to use them do I need to strip the bark off early or let it fall away naturally. Do they need to be seasoned and for how long after cutting?

How much prep work do they need...sawing off branch stubs planing sanding?

The lady tells me the tree is a son talay does that mean anything..softwood or h/w looks like sw to me.

Interesting to see the price variations on old trees beams etc. Today i was quoted 7k-15k for some 12/14" diameters; sone were 5k each some were 1k per metre sone were 800 per metre if you collect yourself. But generally 5k for a 5m prepared or secondhand mortice riddled post.