I know the back is thin...but have hubby drive a few finish nails through the backing, into the edge of the shelf (I'd predrill, as the particle board is easy to damage, and a bugger to nail into). This will help a lot. The dowel from floor to center edges of the shelf will help also. One on each side...your metal brackets act like a spring to some extent...and abouncin' your machine will go...just like kids on a bed.