Have you tried the Slidelock?
 

If you have used the slidelock to prevent ruler slipping, please let me know your opinions as to how successful (or not) they were. I'm looking at them because I have problems with accurate cutting and thought they might be helpful. Thanks.
http://quiltersslidelock.com/slidelock-models/

I've had one ever since I cut my finger with a rotary cutter. I bought it for safety back when it was only available from an Australian website. Much cheaper then the ER bill and follow up even after insurance. I have both sizes and will not cut with a cutter without it. I put it on top of my ruler, I don't use it as ruler. I don't know why anyone would cut with a rotary cutter and not use a safety device of some kind. My guild has a rule that anyone cutting has to use a cut resistant glove, a ruler grip, or the Slidelock. The guild has all three available to use when cutting . Having to call an ambulance twice because of bad cuts (one member almost sued the guild for no safety device offered, yes it can happen) the guild makes no exceptions about having to use a safety device when cutting in their meetings.

I tried it out and started cutting with my ruler the way you cut with one of these rulers whihc to me is backwards. The one thing I disliked was no lines to use to line up to cut. Do you have a friend who has one and ask to try it out? Test driving stuff is a great way to find if it fits your needs.

I love mine. Use it on top of my June Taylor mat to cut strips. It is the best thing I have found for keeping that mat from slipping. I agree it's not great on its own. Like the tip about using it on top of a ruler; will try that.

I use both sizes all the time on top and in conjunction with other rulers

It originally was a safety tool and the instructions were to use it on top of another ruler. It works best that way, so why so many started using it as a ruler is odd and is not the intended use. The makers I guess went with the idea it stopped miss cuts instead of safety as most won't buy a safety tool that is pricey.

I have both sizes and they're okay. I wish they were a bit wider because when I'm holding the handle, my hand is still in the way a little. I am confused about how it works on top of another ruler since the slippery-ness between the plain ruler and the fabric is the same either way. The slidelock has rubbery balls that would never even contact the fabric if it's on top of another ruler, and the other ruler is still slick on the underside.

I love mine and am considering buying the smaller one. I have used it on fabric and another ruler and never had a problem.

Love mine.....best thing since sliced bread