What are rules about adding commands to mfsroot?

[PeterSteele]

We're doing a scripted sysinstall via a PXE boot server and need to add some commands to the mfsroot image. I've done some quick experiments though and it doesn't seem we can use standard FreeBSD binaries. In looking at the commands that are included in mfsroot by default I see that they are all the same size, so clearly there is something special about them.

I've added a couple of commands that we need but when these are run through the install.cfg "system" command, they fail. However, if I exit from sysinstall and enter a live shell, the commands appear to work fine.

So, is there anyway to add additional FreeBSD commands to the mfsroot image that can be run though install.cfg?