re: Designing a mobile cart.

I've tried the Sketchup upscale trick but I invariably forget and enter something at the original scale and it disappears because it is microscopic at 1000th of the scale I should have used.  After starting over a few times, I have up.  I would rather learn something new than screw with that issue (bug).  Besides, the parametric paradigm of the more modern CAD platforms is amazing when you do it right.  Onshape has a bunch of free online lessons that even include exercises to drive home the concepts of each lesson.  All of the lessons that I have done are excellent and even geezers can follow along.   None of the lessons are very long so it doesn't take long to learn enough to start design things.