Having bought 80mm extrusion, combined with not having a tall gantry you have the potential for a very strong machine.
I notice you have chosen TBR rails over SBR, which is good since they are stronger yet significantly more expensive as you can't get them from China (eBay seller linearmotionbearings2008). Using supported rails on the Z-axis and swapping the rails round such that the rails are mounted to the Z-axis would make the Z-axis significantly stronger since the overhang is reduced.

Minor point as it's probably only temporary anyway - I'd solder the motor wires since if one pulls out of the terminal blocks whilst powered there's a good chance the stepper driver will be broken.

Still, for V-carving you'll be fine.