I got this one a few weeks a go: http://www.sw-box.com/Stainless-Steel-Back-Cover-For-Iphone-4-Silver.html I instantly realised that receptions was hindered by the cover, where I used to get 5 bars I would get 3-4. Wasn't really bothered as there was still adequate reception. I soon realised though that in areas where I got 1-2 bars I now got instant searching and then no signal, with the phone just sitting there. So are there any metal back covers that don't hinder reception? If there are what is this one missing?
Im thinking the designers of the IP4 may have had this in mind when they chose glass for back covers instead of metal. The IP4 does not have a rubber ducky antenna so the reception is based in part on the design and the rest on the side antenna arrays. Glass is invisible to the antennae but perhaps the metal or composite is not. I would go back to stock myself.
I guess you are right, part of the signal is being blocked. I went back to stock. As nice as the metal back is, it's not worth the hit in reception.