I've read (read: glossed over, because it's largely irrelevant to most brewing) about ways to calculate diastatic power, but from what I gestalt, with modern highly modified malts, it doesn't take much base malt to convert most adjuncts. If you're wanting to be conservative, perhaps use some 6-row barley (which has more enzymatic power than 2-row).
Packaged: Red X Weimea SMaSH
Recent Meads: Mead Day '11 Ginger Metheglin, Mead Day '12 Traditional (orange blossom) Mead, Simple Cyser '12
Secondary: Why do I keep this line here...?
Bulk Aging: Cocobochet, Wild Cider, Simple Cyser
Planned: Hop Metheglin #3 (NZ hops), Trad. Gesho T'ej