If you have not already purchased it do yourself a favor and buy Randy Mosher's book Radical Brewing. It's a great book and includes a number of chapters on using unorthodox ingredients, including a chapter on other herbs, one on fruit, and a chapter on alternate grains to use in beer. He includes spelt in the chapter on grain and has a recipe or two that use spelt for a portion of the mash.
I've not used spelt myself but I've always consulted Mosher when I'm branching out into uncharted territory in terms of ingredients and find him a reliable guide.