[NTG-context] Register layout

Quick question - how do I alter the width of the hanging indent of a register entry which is too long to fit on one line? I want to differentiate sub-entries, which each have an indent of 1em more than the previous level, from the indentation of longer entries, which by default is also set to 1em. In other words, for two entries: "a short entry" "a sub-entry" "quite a long-winded single entry" I would like the layout (please view with fixed width font): a short entry a sub-entry quite a long-winded single entry I tried putting \hangafter=1\hangindent=3em into the deeptextcommand of \setupregister but no change. Are there any hooks for this sort of thing? Thanks, Duncan