I myself got recently a monofin "Freediver" with Omer foot-pockets, manufactured by Leadefins. I followed a review by D. Lee in
www.apneablue.com, who gave a high ranking to this fin. Though being quite new to monofinning, I felt comfortable with from the very first moment. It's not heavy, and the stiffness - at least for my stature - is sufficient. The fin isn't cheap (€ 219,--) but given its characteristics may be worthwhile considering it.