If you use the OEM grill as the "stopper" then your adapter/spacer will work without any adhesive/glue to the R4 cone. It is no different than what the Dynamat does but looking and working better...
-2012 E92 M3 Jerez Black/Rust Brown, M-DCT: September ED
-2008 E90 M3 Melbourne Red/Bamboo, 6MT: Gone
-2007 MK5 GTI United Grey/Grey, DSG: Gone
-2004 E46 M3 Carbon Black/Cinnamon, 6MT: Gone
-2002 E46 330i Orient Blue/Natural Brown, 5MT: Gone