I would definitely put something underneath if it was for any length of time. I knew it would be quick to make my measurements. A dolly is in the plans (after the ballast).Congrats.
Those pins should clean nicely, but even if they don't clean up to your satisfaction, they are pretty cheap to replace.
About 35 bucks each if I recall correctly.
Judging from your picture, I would also consider putting something under the "main body" for when the hydraulics bleed down on the outriggers.