Be sure to plan for an eventual 4th axis. On the 1100, the old 4th axis had a stepper motor that would stick out when the machine was homed. If the 770 has the same problem, then you'll need to redesign your enclosure to allow clearance.

Where are you getting your aluminum extrusions? I've been thinking about a similar enclosure, and haven't found a good source for the metal yet.

Frederic