Sorry for putting the BD in! it turned up at the right price, so i thought id try it..... 
Would a BD be good in the bridge, or still too dark?
it will be alot better in the bridge. even if you move the black dog on, its good to have a reference point. I think you did the right thing buying it.
the wood Gordon Smith uses (cedar I think?) does sound different to mahogany. Spikier mids and a bit more bass.
After trying the black dog in the neck and having it too dark, I would definitely say go with Riff Raffs in the neck position.
edit: I quite liked the normal Gordon Smith pickups until I tried something else in the same guitar. I like the attack of them, but they are a bit flat.