Max,I'm just happy that I might be a little help. I really enjoy learning a little along the way myself, like about your poplar. And the thanks and the feedback make it really great.
I do have a sneaky suspicion that you might want to be looking around for at least a few boards that can be cut to match your siding, assuming that you are going to replace with poplar. The guys and gals at http://www.woodweb.com/~industry/saw-dry/index.html may be able to help on this. Your originals probably never saw a kiln but ask John Leeke about this too. If my assumption is correct, you probably want to put up pretty freshly sawn siding also or you might end up with a lot of airplane propeller stock. At least you would have a lifetime supply of whirly-gig blade material.