I have one of these as well. Got it when we had our first child. I stopped using it after a month or so.
We went to a 'family fair' at a hospital on our area. They had lots of things related to safety, including the fire department checking on car seat installs. So we volunteered have ours checked out. I was happy to do so since I think I did a great job of cinching ours in.
One of the firemen checked it out and saw we had the protector. He cautioned me that those really decrease the effectiveness of the car seat. He said that no matter how tight you cinch the seat in, in a collision, they tend to allow the seat to slide. Now I can't say for sure how true that is, but he seemed to have a hint of gravity in his voice about it. (He also cautioned against other accessories like the mirrors on headrest so you can see the baby in a rear facing car seat. Since those can become projectiles in a collision also.)
What he did recommend, and what I do now, is to use is shelf liner paper (e.g. Contact paper) like the one in this link:
Amazon.com: Duck 1100731 Non-Adhesive Select Easy Shelf Liner, Jumbo Roll, 12-Inch Wide, 20-Square-Feet, Taupe: Kitchen Dining
He offered that it won't do quite the same level of leather protection as the protector would, but that it would help soften the sharp edges of the car seat's base. I had some at home and tried it. And I can tell you it really is much stickier. As good a job as I did with the protector, it still could be moved if I really used force. But with the shelf liner under it, it really didn't move.
Now this also won't do the job of 'catching sticky stuff' and it won't distribute the wait like the protector would. But I've been using the shelf liner under my car seat since as it does seem safer with a bit of protection.
I guess you could try putting a sheet of shelf liner under/over the protector, that might add some stickiness. I never thought of that til just now.
Anyways, I just wanted to share my comments on the protector and what I do in my car as an alternative.