What's the activity level for Members, 60 or 70 ? Both of the numbers have been mentioned in this thread.
And I think that spamming up the rank should be limited by another parameter. The formula
activity = min(time * 14, posts)
should be :
activity = min(time * 14, min(posts, qposts))
where
qposts = floor(min(words, posts*20)/20)
qposts ~ a count of 'conditionally' quality posts
words ~ total sum of words in all user's posts
20 ~ minimal amount of words in one post to be considered as a quality input
20 words makes hardly one decent line, so it's not a lot, could be higher.
That would stimulate people to actually write something and avoid polluting threads with statements such as
"i'm in ! great dev !"