[AustinSchuh]

Grabcad is pretty cool. I only run Windows in January and February, but it let me see what you are doing and give some feedback.

You really need some flanges on both of the bottom edges of your drive rail. The bottom edges are quite weak right now. While you are at it, tie those into your belly pan. They will bow under load.

The flanges on the top of your frame rail are way too short. They look like 1" flanges or shorter. We have bent frame rails that had 1.5" long flanges with another flange off the back side of that flange for even more strength.

Also, any reason why you are using angle iron in the corners rather than adding a flange to the side rails?

Nice work making the two side rails the same part. That will help with machining. Most people miss that one.

Consider adding access holes in the outside of your frame for bolts holding your transmissions on. Being able to get a wrench in there easily is very useful.