You maybe know that Black Diamond sells the lower carbon fiber pole from their BD Adjustable Probe Ski Poles for $11 apiece (as of March '09). These fit into the upper part of the current (mfr'd. after fall, 2007) BD Whippets with no adapter needed. That way you'll have a pair of BD Adjustable Probe Whippets. Make sure you ask Black Diamond for the lower carbon fiber sections as a male and female pair so they will screw together to make a probe. One note of caution: When you replace the 115-140 Whippet lower aluminum section with a 115-140 Adjustable Probe Ski Pole lower section you will have a pole that is about 4" longer when you compare length at the shortest and longest adjustments. That is, the range is bumped up about 4". If this is a problem (pole becomes too long, then you can opt for the shorter 100 - 125 cm lower Adjustable Probe Ski Pole section from Black Diamond, also for $11 each. These lower sections are not sold by backcountry.com (I wish they were)--just Black Diamond mail order--but you should definitely get your Whippets from bc.com. They just knocked $10 off the price and you can't beat that, plus they're the greatest retailers anywhere.
I hope this is clear. I really got confused writing it, but I'm sure I got it right. As others have said, a dedicated primary probe should always be in your pack.