FastCGI buffer optimization when max buffer is 36MB?

First, I have been following and using RTCamp’s resources for a long time. (Thank your Rahul!) Anyways, we are running WP but for a blog, secondary to our X-Cart (PHP) shopping cart. I ran the awk commands and I have a tiny bit under 36MB for a max request and 38k for the average request. So I decided to set the buffer as 42k, and I just divided 36MB by 42k, I got ~857. Setting a 856 42k buffer sounds like a lot to me. Any advice?