In High resolution console on FreeBSD I mentioned a particular way of setting the VESA mode for syscons, but a post on the freebsd-questions mailing list mentioned a different method. Instead of setting the allscreens_flags="MODE_325" in /etc/rc.conf, you use the /boot/device.hints file.

Putting the following items into /boot/device.hints puts syscons into MODE_325 (1280x1024x32 on my VirtualBox installation).

hint.sc.0.at="isa"
hint.sc.0.flags="0x180"
hint.sc.0.vesa_mode="0x145"

This doesn't put FreeBSD into this mode as soon as the kernel starts booting, but it does as soon as the sc driver is loaded (which is much sooner than rc.conf is processed). As a result, a significant portion of your dmesg is available in your larger console.

Not critical, but neat.