Was about to get a toy- then I did some research...

[AndyUK]

If I have two steppers driving the long axis, should I input half the total weight of the gantry in the calculator?

Good question. It's a topic worth discussing. My personal view is that you should double the screw inertia (you have two screws to spin), but also double the motor torque (two motors, after all!)

Also, you don't happen to have any comments on the frame?

Keep posting and I'll comment when you've posted some pictures of your design :) I'm quite a fan of extruded aluminium profiles, it makes the whole thing a lot easier - my gantry went together in hours, my steel and epoxy X axis took weeks. I don't think you can 'overbuild' though...