To ensure the engineering folks at Van's receive your report, do the following.
There is a reporting procedure (required by ASTM standards) in the RV-12 Maintenance Manual section 16-1. Safety issues should be reported so there is a record.
'Safety Alert' (in subject line)
For this issue include your total time, a qualitative description how loose each engine mounting bolt was, and whether or not you added locktite.
SEVEN of us NOW with 85 to over 200 hours have found LOOSE ENGINE MOUNTING BOLTS.