If your bow is a centershot, you can pretty much use whatever spine you want. The spine really comes into play when the arrow has to bend around the bow when shot. I've always shot wood arrows, and have never had one break. A visual inspection is usually all you need to check for cracks. You can flex them some without them staying bent, but you really don't need to unless you're trying to straighten them.
The test kit would be a good place for you to start. With a Savanah, I'd try the 50-55# range to start with. Or if you know you're gonna cut them down quite a bit, then just go with the 45-50# range and after you cut them the spine will get a little heavier.
Joe