can mating a whippet with a husky make a faster sled dog

Actually, many mushers believe that you *can* "improve on a husky by creating a mutt" -- thus, the modern-day Alaskan Husky.

The Alaskan Husky was developed using Siberians, Native Village dogs, and anything else that would make it faster. Winning times for the Iditarod continue to shorten every year, due to the fact that mushers are trying to make faster and faster sled dogs. With average temperatures much warmer than they used to be, coat is no longer as important -- in fact, some of the heavier-coated dogs are now at a disadvantage because they overheat. Plus, you can always throw a Cordura jacket on a sled dog (BLASPHEMY, IMO!) and keep it running if the weather gets colder. Look at Jeff King's dogs. They are Alaskan Huskies with Greyhound and Pointer blood. They have no coat.

http://www.huskyhomestead.com/jeff_king_.

As for feet, many of the breeds incorporated into the Alaskan don't have the feet to run 1000 miles on ice and snow. Modern day mushers don't worry about this -- technology has given them cordura booties and specially designed salves/glues to deal with bad feet.

In the lower 48, sprint races are common due to the fact that the distances for longer races just aren't there. These races have produced "Houndskies" and "Eurohounds", sled dogs that fall under the heading "Alaskan Husky" but are more than 50% hound and short-haired hunting dog (usually pointer). These dogs run 4, 6, 8, 10, or 15 miles at a time, and are built for speed over all else. They don't need good coat, good feet, and only enough trail sense to know when to take a turn. Examples: