Chain saw sculptors?

OK, a few jobs involving 'Wood' at the moment. I have two 200mm square Oak gate posts. I probably over egged the dimensions, and I had every intention to shape them into a curve or a point, but couldn't quite figure the geometry in relation to my 185mm circular saw... ok I've been procrastinating.

Anyway, I was awoken by the diggermen on Saturday morning, who have arrived to install the posts. They are now upright. 1m down bedded in concrete and looking colossal.

Would a chainsaw sculptor be my only option?

Yes but if you get it wrong what are you going to do? Better leaving them.

Consider temple caps or finials, maybe? 8" will be somewhat restrictive, but you never know!
John

You need to speak to someone who is used to working with big pieces of (preferably)oak. Green timber framer etc. Nothing against chainsaw sculptors, but what they do is very "free form" and as already said you only have one shot at it.
As John says a cap of some kind might be the answer, and would have the advantage of being face grain up rather than end grain and so being less porous. Again an oak framer may be able to help you.
Another answer might be to run a big bold chamfer all around the top. Mark it out first if you do that. I'd use hand tools rather than power tools, because any mistakes are less "instant", and tend to be smaller. Obviously whatever you do you need a safe platform to work off.