putting ypur posts into the consrete is asking for trouble down the road.for example, here in Florida we use cypress a lot for fence posts and when placed in concrete even with sloping the top it lasts maybe 4-5 years.you will never be able to keep out all the moisture. however, when set on top of a concrete footing at the bottom of a 3' deep footing with a gravel and sand back fill it will last almost indefinately and also be as solid as concrete. if strength or resistance to up lift is your goal try anchoring metal post clips into the footing and bolt them on to the post.
