To add a bit to what KevinF and others have said, people (especially those who stay on groomers) are finding adequate stability in shorter lengths. In addition, many of these people have begun to prefer skis with tighter and tighter sidecut radii so that people can continue to carve (or come close to it) in tight situations, or simply for the thrill of high-G's at comparatively low speeds.
The tip and tail get unwieldly large in the longer lengths if the designer wants to maintain the same short sidecut radius. Mfgrs have felt that skis with such large tips & tails would be of less interest to people, and in almost all cases, simply haven't offered the longer length versions of models with tight sidecut radii.
For example, a 16 meter sidecut radius would have to have dimensions around 103/65/93 in a 165 cm length. The same dimensions in a 185 would produce a sidecut radius of approximately 20 meters. To keep the sidecut constant at 16 meters at 185 cm length, the tip and tail width would have to go up to around 112/65/101, a substantially larger ski, with substantially higher swing weight.
In the past couple of years, skis like the 9.12 (115/65/100 @ 170 cm, 12 meter sidecut radius) have been introduced, and have become quite popular in spite of a shovel as wide as that of many powder skis. According to Peter Keelty, the longest length Atomic offers in this model is a 170. My guess is that over the next couple of years, we will see the mfgrs explore what people will tolerate in terms of larger tip and tail sizes.
Tom / PM
[ March 18, 2003, 08:13 AM: Message edited by: PhysicsMan ]