If I can get a LM-3S, a sugar cube speaker and a KA-4 in a P2K S3, you can do a SW1.
I had to remove all of the extra weight, and cut out part of the cab interior to get it to fit, but I got it all in there. It's tight!
Still moves 12-15 cars through my curvy yard lead. Much more and she gets cranky. I'm thinking of adding some moldeable lead to various visible nooks and crannies (like behind the steps, etc.) to add a little bit more weight.
There are no pictures (I'm not ripping it apart after I got it all to fit!), but there is a description in the RPUG files.
Can't wait to attempt the Rapido SW1200RS and GMD-1s...I hear the SW1200RS are not designed to be opened up easily.