Yes you can cut it, but I wouldn't lop off a few inches. Instead I'd start off with maybe 1/2" off each end. That way you won't end up with a new riser bar that's too short. A hacksaw works and if you give yourself a reference line it'll come out fairly straight. I used a pipe cutter (<$10 at Home Depot) and while it leaves a slightly raised bit on the ends I just file it flat in no time at all. Some folks use a Dremel, but it goes through a few cutting wheels using that. If you have a metal cutting blade on a table saw that will work too. All of those ways work fine, but if you don't know how to use any of the tools properly ask someone first as it's not as simple as it seems if you've never done it before.