I think it looks good but I would caution you about the attachment points. When you take impact, all of the force is going to be against those points so make sure you consider where they are located and that they have enough material backing them to handle the impacts.
Also, I can't recommend these enough for attaching bumpers:
http://www.mcmaster.com/#90985a303/=u6jmdg
They are kinda expensive but you can re-use them year after year.
Our team was running drills the other night and those things can lead to some seriously short bumper changes (30 seconds and under). We're quite happy with them.
Good work on the design though and addressing bumpers before the 6th week of build season!