Yup, yup ... sure the rear tip has a huge effect when going forward.
It has just about as much effect as rear spoilers do on cars that will never go over 70 mph.
means "I'm joking - big time" (added in edit))
In all seriousness, tho, I think that there are effects, but whether or not you could call them "benefits" is all in the eye of the beholder.
The K2 Enemy is a good example to allow one to compare the performance (going forward) of a TT with that of a very closely related non-TT. My recollection is that the Enemy is just a modified verion of the the older K2 Explorer. Here's what happened when they made the various modifications to the older ski to turn it into a TT.
The simple act of turning up the last 10 cm of the tail of an Explorer decreases its effective length, so, the effective length of a 173 cm Enemy may be approximately equal to the effective length of a 167-ish cm Explorer.
In addition, I'm pretty certain that k2 also softened the next 10 or 20 cm of the tail a bit so that the tail would not be too stiff when skiing switch. This also makes the Enemy handle differently than an Explorer (even if you compare two skis of the same *effective* length). The softer tail of the Enemy is better for slithering around in a mogul field, but not quite as good as the Explorer as an all-mountain board. The bottom line is that its not the tip itself that does much to the performance, its all the other little changes that usually go along with it.
IMHO, the guy in the shop was BS'ing you.
Hope this helps,
Tom / PM
PS (in edit) - FWIW, I'm an old fart that would never dream of doing outrageous things in the park (or the air above the park -grin), but yet I ski a 173 Enemy TT on many days. Its a fun, versatile ski, great for slower lines in the bumps, trees, and general noodling around. However, if I can help it, you won't EVER catch me skiing it: (a) going stupid fast; (b) on ice; (c) demoing ultra tight carves; (d) in really bad slop or deep pow.
I think SpinHeli of Mammoth also skiis (or used to ski) an Enemy as his everyday ski, so he might be able to shed some more light on TT's as well.[ August 09, 2002, 12:02 AM: Message edited by: PhysicsMan ]