Fred,
I currently use a combination of Rubber mulch (only 3" worth) Rubber mats (1 between the rubber mulch and duct seal, and another for the face of the trap)
and about 50 lbs of duct seal in a 12" by 18" by 6" enclosure.
I built the back of the enclosure to be bomb proof but it is not needed and the trap is relatively quiet even with the 30 cal.
As an update I sold the Crown as I just had to have a RAW LRT in 30 cal that became available.
I really did like the Crown but only could keep one and the RAW is just put together a little better.
GT,
It is a Bald Eagle with the windage cable removal modification.
I have actually modified it even more since that picture with a Randolf adjustable top and a Sinclair elevations speed screw.