Like Ian asks materials to cut will help but I've got a few why's.?

Why supportedround rails.?
Why 1604 ~(Do you mean 1605 ballscrews)
Why that size Profile.?
Why is there No bed.?

Got few a suggestions as well. Would make it so the Gantry sit directly on the bearings rather than between the bearing with brackets. This will make it easier to build and setup along with making accurecy easier to find. The way you have it will be much harder to setup without causing binding to bearings etc than sat directly on bearings.

Don't wrap a box around the gantry it doesn't add any strength really and makes setting up harder with bigger potential for causing binding bearings. The extra weight just means less potential acceleration.
Use thicker Rear Z axis plate as 10mm isn't enough and any resonance here will transfer to the finish quality.

Better if you can get the ballscrews down the side out the way as being stuck up high like that they are open to being lent on or caught with material when loading etc.

You don't show any lower frame so it's hard to tell what you thinking here but just bare in mind the base is the foundation for everything else so if this isn't accurate or strong it will impact the rest of the machine in a negative way.!!