Most of Hot Melt Glue came loose within several months, so I re glued them using Marine Goop Glue, which is much stronger and lasting 3 years so far in very cold -20 degree Celsius and +45 degree Celsius weather. I have Tupperware in engine compartment , which I keep spare light bulbs. it has been there for last 3 years , but has not had any water leakage or melting problem. Subaru engine is Flat Boxer Engine , similar to air craft engine, most of engine are in bottom half of Hood and there are a lot of opening on top of engine between Hood. and Exhaust come out of Bottom of engine, so it may be different from other cars.