Steve will be along for the dial-in, but you're correct in suspecting that temperature can make a huge difference to the impact of a static fuel mix (power and mileage per gallon). Cold air is denser, so there's more air to the same fuel, so cold temps lean out the fuel mix. Warm temps do the opposite and richen the mixture. Incidentally, the same is true for altitude - higher elevations = less air = rich mixture, so if you're jetted OK for sea level, you can have the bike barely run at high elevations and if it's hot in the mountains, you're going to start fouling plugs (if it's cold, then you're in better shape).
You'll never have "perfectly" dialed-in foam for every temperature and/or elevation and/or barometric pressure - only fuel injection can do that. Hard to know what sizes of foam to carry for different temps (20 degree differential? 10?) without a dyno, or consistent recorded observations resulting from experimentation. Certainly, you could pull the foam for mountain riding.
Ideally, you'd pick a single foam size that was perfect for the mid-range of your usual riding temps and elevation, and live with less than perfection otherwise.