The colorado/willow combo is like trying to get the best of both worlds. It serves 2 purposes, the first one is that it'll give a little more vibration to the bait and the second is it'll let you fish it slightly shallower at a slower speed because the small colorado will help give it some lift. A double colorado is a shallow vibration bait. you see this mostly on heavy baits so you can retrieve it faster without it lifting out of the water. The size of the blade on the wire shaft depends on what you want the bait to do, like fishing shallow but at a slow speed then you want to put a colorado blade on front but if you still havt fish it too fast to keep the bait where you want it then you need to go a little larger, if you want some vibration but don't want the bait to lift too high a smaller blade, etc. Blade spacing works almost the same way, if you use a larger front blade, then you will want to have more space between blades because the lager blade will displace more water which can have an adverse affect on the main blade. Use your imagination and try out some different combos, you'll see what works and what doesn't plus you may find something that the fish find unable to resist. Good luck.