Guys I think we need some babysitting... we are pretty far off topic haha. But, to add to the off topic-ness, why wouldn't just installing grommets in the tramp and running the shock chords through it work? Is that just class illegal? That way, the shock chords run above the rail grip instead of below them.
Now back to on topic, I prefer rubber. Many guys have expressed concerns about mildew/mold growing on carpet grips and that they retain water, making your boat slightly heavier and therefore slightly slower for racing (if you race the boat).
If you do decide to go rubber, I currently have this on my boat, but I wouldn't recommend it:
http://www.murrays.com/30-210.html The reason I wouldn't recommend it is because the width of the grip they provide you with is okay, but in sufficient to cover your entire side rail. So, when the shock chord runs past it it slowly chips away at the outermost edge of the side rail grip.
Instead, I would recommend purchasing this:
http://hydroturf.com/products/Sheets_of ... urf?page=1 Other people I compete against purchase it "by the sheet" and cut it to size for their Hobie 16s and their F18s. The girl I sail against who goes to Hobie North Americans every year says this stuff puts up with the shock chords rubbing against it very well. I've only heard one bad thing from one F18 sailor who bought the camo pattern. He said that the black/white camo pattern can oxidize at different rates among the colors, so the surface eventually becomes uneven. To prevent this just purchase a solid color.
When installing, be sure to have an ample amount of C-clamps and some spare pieces of wood to hold the sheets in place while you wait for the contact cement to dry. I would also recommend a roller (like a kitchen roller used for baking) of some sort to help roll the bubbles out from underneath. This will make for a better stick.
-Evan