What pain are you trying to prevent?

I recommend calling them and asking your questions. They're very helpful. IIRC, ISM offers a 30 day trial. Or you can try Amazon - if you are a Prime customer, I know there's a vendor who offers a free return.

When you ride on an ISM, your really important bits are in from of the horms, and you rest your pubic rami on the horns. There's very little pressure on ischial tuberosities. Check out the doc on the ISM website.

Like any seat, if the ISM works for you, it just plain works. If it doesn't, it hurts.