If you are concerned about range on the 350, like we are, then higher is usually better. I don't have the exact numbers in front of me right now, but you will save an additional 20%-30% of fuel by flying in the RVSM airspace. An example, if you fly @ FL220, you'll burn approximately 400lbs a side. At FL330 you'll burn approximately 300lbs a side. That's flying it at 800 ITT. You're TAS at 220 is comprable to the TAS at 330. The optimal altitude for TAS for the 300-350 is around FL260-280. We RVSM'd our plane. My selling point to the boss, beside's range increases was this: If you go long distances in the 300 or 350 you want to be able to get above the weather. A 1200 mile flight, which we do often, will be very uncomfortable and frustrating if most all of it is IMC, icey and bumpy, especially if reports say that 2000 feet higher, say to FL300 would put you in the clear. We also found out that ATC sometimes is keeping the upper 20's for non RVSM'd jets like the older Lears, thus keeping King Air's in the mid to lower 20's. Not always but sometimes.Good luck.
