Mountain Biking - Bike sizing for Rocky Mountain (do they tend to be sized short?)

I found a used 04 RM Hammer for a good deal online. I am 5'10/11 and 170-175 with an inseam of 32. The bike is a size 17.5. The thing I am worried about is the size. I looked online at Rocky Mountain bikes and they have the stand over height of 743mm which is like 29.25 in, so it should give me a good 2-3 inches clearance which is perfect. I am sorta between the 17.5 and 18.5. So the 18.5 is just like 3/4in higher than the 17.5. It also has a top tube length of 565mm. I heard someone tell me that RM tend to be sized shorter than other companies. So a 17.5 in a RM would be more like a 16 in another company. Is there any truth to that? Or can I get away with the 17.5?

Nice they fit small, the top tubes are tiny. A large switch is tall and short.

Nice they fit small, the top tubes are tiny. A large switch is tall and short.

So does that mean they run a size or so smaller than other companies?

Have you ridden it? Try it and see if you like it. Some people like their bikes sizes small, with loooong seatposts, others like them low and long. If it feels good, then who cares whether others think it fits you, all that matters is you like it.

The sizing on the Rocky hardtails tends to be on the small side. Go to a dealer and take one for a ride

So does that mean they run a size or so smaller than other companies?

Not really, it means their geometry is different. A Large switch was tall like any other large but the ttt was shorter than what a large should be imo.

Would you say, compared to your legs, your torso is relatively short or relatively tall? Looks like the Rocky's effective top tubes do run shorter. If it's close, you can always compensate with a longer stem. You also have to consider your riding style. Do you like to be stretched out over the bike, you do you like more of an upright position?

You might also consider getting someone to help you take measurements and plug the numbers into a fit calculator like those at:
http://www.wrenchscience.com
http://www.coloradocyclist.com/bikefit/
http://www.competitivecyclist.com/za/CCM?PAGE=FIT_CALCULATOR_INTRO

On the Topic of RM bikes. I am trying to sell a 2000 RM6 (large), oddly I have had no local interest so far.
Any suggestions?

I have placed it on CL and ride monkey thus far.