I've been toying with it a bit now. Passing the tag end through the first loop twice materially aids in its security, but either way it is the very booger to untie after a load has been placed on it. Even my idea of forming a pull by passing a bight instead of the tag end through is a bit hard to untie. This in polyester rope; I haven't tied it as a non-slip loop in monofilament line yet.
