Keep in mind that snakes can actually dissolve bones which is amazing to me! Probably won't have an issue digesting a little coconut husk.
When shopping around for coconut substrate always look at the final expanded volumes when comparing prices. One of the reasons I went with Repitchip is that it expands so much. Just three expanded blocks will fill a 55 gallon drum! I have yet to find any coconut husk that is cheaper let alone a high quality coconut at that volume for that price (at current prices it's about 34 cents per quart delivered to your door from ebay). If you can pick it up at a reptile show you can cut down on the shipping costs and it's much cheaper.