I think volume is important however I think that content is equally as important. I don't think anyone here would take issue with you folks deciding on the over-all merit of posts ie if someone posts a question and then someone else posts a relevant answer, the quality of that answer should weigh in maybe even more than the count of 1 you get for posting it. Like someone asks "What's the best way to boost NO pre-workout" and someone responds "Have you tried Arginine?". Someone else responds 'Well you should try Agmatine, at X dose and try taking it x minutes before work-out and stack it with x and y and if you aren't seeing the results you want boost the dose to here safely etc etc" you get the idea. I think that answer should be weighed more heavily in addition to the credit for the volume count.
Some people can attend the board more than others so in this way the ones with less time to attend the board won't necessarily get punished in their chances to win a prize. If the quality of their content makes up a lot for a lower quantity then I think reward for that is good but you guys will have to decide the ratio/merit etc.
Also, rewarding the quality of the posts will only benefit the quality of the board by perhaps instilling a sense of actually writing better content every time you post, and definitely not saying there is any issue in that area but any benefit will always be good/better for the community over-all. You definitely don't want people being overly verbose just for the sake of it, and some of us will yak your ear off given an opportunity ( looking in the mirror here lol) but again, that will be for the mgmt to decide where the sweet spot is in any given post etc.
Anyway, as a really new guy here I'm slowly working my way through the already posted content and trying to post in where I can contribute something of value but what I have seen so far is a lot of really good content. I think the contest will only make that better, and a little bit of friendly competition driving folks, now and again, is always a good thing IMHO.
Cheers