As long as it's epoxyed on there, it shouldn't matter how thin it is. I've done some tests on the relative durability of the handle materials I use and micarta is unquestionably the best. I used a 125lb anvil and a 2000g german blacksmith's hammer with a 24" handle. Striking the materials on the anvil with a guided fall of the hammer from above my head, I counted the number of strokes it took for the various materials to fail (I used a couple different kinds of wood, plexiglass and micarta — I've never used G10). The wood completely disintegrated in under four strokes. The Plexiglass cracked (but did not dissassociate) at around seven strokes, then shattered violently on the following stroke. Micarta took over ten strokes before it broke. Micarta is also quite flexible, so thin parts are unlikely to break even if they are not epoxied. During my tests, the micarta never chipped, but eventually just broke or delaminated.
I have no doubt that micarta would be perfect for your karambit.
A friend of mine used a bowie he got with a dymondwood handle for a throwing knife. It held up a lot better than wood, but pretty quickly came apart.
- Chris