[R-390] Receiver dust covers

[Perry Sandeen]

List,
I did notice less noise on my R388 with the top cover on.
All the R388's I have are missing the bottom cover as well as almost all I've seen on Ebay.  
I don't know how much difference it makes with it missing but I suspect it may be substantial as the sectioned modules have many screw holes for fastening one down.
Does anybody have experience do a shield-no shield test.
Regards,
Perrier