I have the Devol on both my bikes , it works great for protection (full wrap/side protection) , but it does reflect a lot of engine noise , as with any full skid plate , especially a Aluminum one , i use a rubber barrier between the plate and the frame ( i cut strips out of a toolbox drawer liner and glue them to the plate where it contacts the frame rails using contact cement), it serves 3 purposes
It gives a cushion between the plate and frame so it does not wear on either from direct metal to metal friction ... it deadens some of the reflection and vibration rattle noise .... and it allows the frame to still flex , since if you snug down a skid plate to the frame it will actually make the frame more rigid and change the handling and feel *harsher feel* of the chassis , the buffer between the 2 allows the frame to flex like it was designed to , but still offer full protection to the bottom case and ignition cover and water pump (it will not protect from direct side impacts, none of the will)
Hope that helped ....
