After thinking about it, I decided the engine wouldn't put all it's weight in one spot like I did with my hand, so I decided to run a test. I got my SD70, TIU and some 30" RealTrax out of storage. I put 3 tracks together along with a terminal track. One of the tracks spanned a 30" section between my workbenches. I ran the engine back and forth several times and while there was a little flex, it wasn't any more than you'd see running on a carpet. I'm still a little concerned about running at speed around O36 curves on the rather scrawny plastic trestles, but that wasn't the question. My video of the test was a little too large to post here, so if you want to see it, here's the YouTube link.
NOTE: I just noticed your post said O48 loop, so you must have changed the design from the version I have.
