It all seems fine as long as the bolts don't come loose. I've run shared-bolt setups like this (sharing bolts seems to be your primary concern, no?) all the time, and never had a problem due to bolt sharing.

If you want extra security, you can put a locknut on the backside of the bottom bolts. Can't do this for the upper ones, unfortunately, but one thing I've found is that a fatter spacer will stabilize the standoff on the mid-blade eyelet, which may be wobbly from flex in a bolt sticking out that far.