Table Dolly Sled rebuild

I noticed some odd geometry in brucethehoon's file when I printed it. I'm fairly new to 3d modelling, so I thought it would be a good exercise to try rebuilding the sled as a cleaner mesh.

[added back my own weird geometry back into the project: updated with a skirt to mitigate warping at the ends, added some minor bevels, and inner voids for added strength & reduced print speed]