Thinking about speed, I decided to create a file for each post...It will allow a good performance to show topics.
What might slow eForum a bit down is it main page, because it is taken from a file where all topics are stored (just its links actually)...
BUT, as I said before, I garantee that eForum has a good performance even under high traffic...Although when I first created this forum I thought on a small site forum system...
Concerning security, I think that a well-designed flat-file based script can be secure, with Apache's help...