David Rowe reported that his UFO (AR 1.27, 12foot span) has an engine out glide similar to a Drifter, the UFO is an extreme Low Aspect Ratio aircraft. Please look at the video evidence before generalisation.Yes, a high CL at 1.27 AR. But it comes with high Cd. Not a concern to Zimmerman because he was designing for powered vertical lift.
We are concerned with Cd and the resulting L/D, from the combined CL and Cd.