Frankly you mentioned a time frame above that has me thinking that you will be really pressed to bring this all together before February. One of the biggest problems with anything made in a mold is that you have to make the mold first. This especially if the gantry is one piece. I kinda doubt that the gantry is one piece but the beam spanning the table is really thin in my opinion
When you posted this i was actually expecting a moving table design to better leverage the mechanical properties of composite materials. With this approach you avoid having to manage moving a heavy piece of structure. That structure would be easy to damage in a composite form.
The only machines I have had direct experience with when it comes to composite "epoxy granite" type structures are some diamond turning lathes used in the optic's industry. Those castings are surprisingly easy to damage and this was with commercially produced epoxy granite castings. Now fiber reinforcement might help some but unless you intentions are to produce a composite based 100% on fiber reinforcement I'm not convinced that the common composite (epoxy granite) materials makes sense in a moving gantry design.
I'm at my laptop so at least I can find a couple of links. For example:
https://hackaday.com/2016/05/01/prec...epoxy-granite/, a long reprap thread:
https://reprap.org/forum/read.php?148,9376. These still are not what I was trying to fine but can be useful.
I suspect how hard it can be driven will come down to what you have in the way of reinforcements. I wouldn't expect much torsional performance from plain epoxy granites. One option considering your tight time frame, is to use epoxy filled steel tubing instead of a full epoxy granite design. This would give you a greater confidence in the mechanical strength of the machine considering the limited time to properly design and model an all composite design.
If your airplane is in a tailspin you have all the time in the world until you hit the ground to pull out!!! If you don't pull out somebody comes by with a bucket to sweep you up.
I don't know how much time you have to devote to this each day but I just find the time frame to be tight. Hopefully some of this build is already underway.