03 Outback: standoffs for heatshield flattened -> hit driv..

I drive my 2003 Outback on some fairly rough roads, and I've flattened two
of the heatshield standoffs on rocks. The consequence is that the
heatshield occassionally gets pushed up against the drive shaft, and makes a
real racket. I've pried the shield back down multiple times, but it often
settles back up against the drive shaft, or just vibrates noisily, since it
is not held in place at two points.

Is this a common problem, and if so, are there simple solutions? The design
seems stupid to me, as the standoffs are sitting ducks for rough roads. I'd
replace them, but they look like obvious targets for rocks. The exhaust
system itself is fairly well protected, and I have skid plates front and
rear.