I am sure this has been asked before but I am hoping someone can address my specific situation. I am an advanced telemark skier that can ski any terrain in most conditions. I am 5'9", 165 lbs. and currently ski Black Diamond Kilowatt (175cm) as my everyday ski, with the Black Diamond Havoc (175cm) as my teaching ski (I am a part-time telemark instructor), and the Rossignol Ravyn (174cm) as my powder ski. All three skis are mounted with Hammerheads and I am on Scarpa T1s. The Ravyn skis very short so I was looking for a new ski for my powder ski. I mainly ski the resorts, with some sidecountry and a little backcountry, so this ski would see a lot of resort use. I understand that the general rule of thumb with rockered skis is to size up approximately 5 - 10 cm; however, 188cm seems like a big jump, and I should be in the 182 - 185cm range. Any thoughts? Should I be looking at another ski to fill this role?

Here's my experience with the 176 cm and 188 cm S7's. I spent about 50 days (telemark w/ 22D Axl's) on the 176 length and and found them too short and too soft for aggressive skiing. I'm 5'7", 130 lbs and usually ski a 170 cm ski. I recently swapped to 188 cm and after 10 days have enjoyed it a lot more, especially at high speeds in chopped up crud where a longer and stiffer ski are imperative. The extra 18 cm length (relative to my traditional 170cm skis) is of no concern and of no consequence, as the 188's still have a 17.5m radius and short effective edge due to rocker. I am rocking the 188's and loving it! If I was 5'9" and 165 lbs, I would not be concerned at all about the 188's and would even consider the 195 length.

Also Alex... S7's and 130's ski completely differently

Check out the Armada JJ 185 (very similar design to the S7) or the Moment Night Train 182 (also very similar design, but slightly fatter).

Line Prophet 130s come in a 186 and have moderate tip rocker, i have them mounted with hammerheads and really dig the combination. However, the S7s tip rocker is much more dramatic so they might ski even shorter than the 186 Lines. Plus I've heard really excellent things about mounting S7s tele, If you ski aggressively, I wouldn't be too worried about the length...you weigh enough that you should be able to muscle the 188s around.