I have seen a top down furler fitted on a MH33 and a MH37 but not on a MH31. I don't see any reason why you couldn't though. Both the 33 and 37 had a small bob stay fitted on a manufactured bowsprit. Here is a pic of the bowsprit on a MH37 and a spinnaker flying on the MH33.Can you fly a spinnaker on the new marlow hunter 31 with no backstay?
Does it have a fractionally rigged forestay?new marlow hunter 31