Well, after a bit of messing around, the BIOS does in fact SEE the drive, so all is functioning well.
It will boot a good portion, but always fails at:
Trying to mount root from ufs:/dev/da0s1a
Manual root filesystem specification:
<fstype>:<device> Mount <device>using filesystem <fstype>eg. ufs:da0s1a
? List valid disk boot devices
<empty line=""> Abort manual input
mountroot> ?
List of GEOM managed disk devices:
Manual root filesystem specification:
<fstype>:<device> Mount <device>using filesystem <fstype>eg. ufs:da0s1a
? List valid disk boot devices
<empty line=""> Abort manual input
mountroot>
See? Nothings listed. I don't understand.</empty></fstype></device></device></fstype></empty></fstype></device></device></fstype>