I have zero experience with underhung arms but, have followed this and companion threads with interest. Some of you may have seen the talk given by Jonathan Carr to a group or audiophiles in which, amongst other topics, he talks about underhung arms., . for those who haven't, here is the link
Jonathan Carr Presentation at The Audio Salon (youtube.com)
Hopefully we can agree that Jonathan knows a thing or two about cartridges, so his opinion on underhung arms should carry more weight that most. See the relevant part starting at 18:40
cheers .