Forming a fenestration unit which may have seismic safe properties and/or fire resistance rated properties for use in buildings and other structures includes edge attaching a panel of any applicable material, in a continuous fashion, to a supporting mullion. The supporting mullion is attached to the panel by means of a bridging element that withstands tension stresses. Single or multiple insert parts may be attached to the bridging element and may be integrally embedded between multiple sheets composing the panel, or attached respectively in single or multiple grooves at the edge of the panel. The panel may be composed of multiple laminated sheets. A laminating interlayer between the sheets will hold the sheets together as one sheet. The interlayer can be a liquid that may cure to a rigid material. Alternatively, the interlayer may be provided between the multiple sheets and the assembly may be heated and pressed multiple times.