I know this is an old thread but someone showed it to me.
I would love to see pictures of the Ramline forend. The A5 and Rem. 11 have barrel alignment rings that are about two inches different in placement on the barrels. The for end holds the barrel in correct position in the receiver. You cannot do this with out modification that I know of.
The replacement buffers and a brownish grey color and you can still get the rivets. BUT it is far easier to install these with a little modification to them and set them in with Poly Choke rib epoxy.
870/1100 extensions can be used from Fred Choate. He can also sell you this in the white and unassembled. I can mount the two shot extensions from him and actually get 7 shells in the magazine tube and no spacer. The 870/1100 is easier to contend with the spacer though.