Arvin (Lonerider = arvin right?),
Go ahead and get the SI's. They are WAY more convenient than clip ins and you've already invested in the heels, so you might as well utilize them. Using the Madd + TD2 SI's in tahoe conditions will be an excellent combo, and I'm certain it wont be too stiff, especially since you wont be charging the gates in that gear. Besides, stiff gear in relatively soft sierra conditions is a good match.