I have added some of these:
http://www.screwfix.com/prods/37601/...0mm-Pack-of-10
to the "unflat" areas inside my RIB. They are absolutely brilliant. All the areas where you couldn't put your feet before you can now use without your feet sliding off. Worth every penny and they do different types/sizes.
Do be careful if your knuckles drag on the ground though 'cause they are quite abrasive......
