I'm definitely no pro (only just started training, myself, and haven't even personally seen a lot of Games), but I would also recommend not going on the heavier/long side of things.

I train with a group who are pretty strong and they brought a monster caber to practice recently. Apparently it was 16 1/2 feet long and I heard one person say it weighed 115lbs and another say it HAD to weigh at least 125lbs.

Regardless, none of these guys could turn it (although one came close and it was really frustrating him), and although I am not sure how many times they've worked with it I had heard no one from their group has ever turned it.

My husband had never touched a caber before and they were all very nervous about him even going near it and stuck close to him while he tried. He had to bail on it twice and barely even picked it one time. I think that was it and they decided two tries was enough, they would get some better cabers for folks like him to practice with. The guy who runs our practices is very good about safety and form, and I could even see how nervous and concerned he was about Christopher trying it. I'm not sure he really wanted him to, but Christopher was determined to at least see what it was like.

Hope that helps at least some.