I've decided that the custom field code is a dead end; the performance penalties are too great for any payoff there might be, and it's far simpler and less time consuming to respond to user requests for minor changes in the db structure than it is to maintain the complexity of the custom field codebase. Accordingly, I've branched the original Adaptive DB code, which supports custom fields, into a branch called customfieldsbranch, and eliminated (as far as I can tell) all custom field-related code from the trunk. I haven't been able to test any of this yet; it's an all-or-nothing thing. But it should be easy to test it with the Manifestoes dev db later this week.