It needs a mild Hyperboloidal Primary to achieve useful but not brilliant results. The glass types are a little unusual but certainly available. Unfortunately, the lenses are large thin meniscii. Performance is excellent. The last option uses three separate elements of standard glasses in conjunction with a Paraboloidal primary mirror.
Performance is excellent.
Because the lenses are single elements, there exists the option of working stock catalogue lenses into the design. The last PlanoConvex lens is a standard Edmond catalogue item and the deep meniscus element may be produced by modifying an M Griot stock catalogue lens. Modifying the M Griot lens so as to utilize the convex surface would be an interesting exercise. Protect surface, hold lens, generate new surface and work it, etc. One thing which will help is that this lens is very much overdiameter to start with so damage to the edge area will not matter.