Stumbled across this article, which some may find interesting if you have not already seen it. Pasted a section from if below for flavour:
To keep the PRHT both light and compact, it’s constructed of advanced high-strength materials. The front and middle section exterior panels are made of sheet molding compound. Interior panels are glass-fiber-reinforced polypropylene. The assembled panels are barely three-quarters of an inch thick yet they provide an attractive appearance and do an excellent job of blocking wind and road noise. The rear window is glass imprinted with an electric defroster grid. To maintain body rigidity with an opening that’s 1.8-inches wider and 3.2-inches longer than the soft-top’s aperture, material thicknesses of the body panels surrounding the opening have been increased and two corner-reinforcing brackets have been added. Closedsection reinforcements also extend from the rear deck along the outer edges of the top storage well. The deck lid changes from aluminum in the MX-5 soft-top to steel for the PRHT to accommodate contours added for an attractive appearance. Altogether, the net weight increase over the soft-top model is only approximately 80 pounds (depending on trim levels), quite reasonable considering the benefits delivered. Minor suspension adjustments were in order to maintain the quick steering response and predictable handling expected of MX-5. Dampers are firmer, rear spring rates are higher, and the front anti-roll bar has been increased from 0.83-in. to 0.87-in. in diameter. Like the soft-top MX-5, the PRHT edition has a wind deflector to block cockpit drafts. A 1.3-inch-high air guide runs the full width of the deflector to reduce the energy of the back draft impinging the driver and passenger. With the top raised, interior noise level with the PRHT is reduced in comparison with the soft-top MX-5. Design changes to accommodate the MX-5’s PRHT are especially gentle brush strokes. To integrate the appearance of the deck cover, an accent crease flows from each door over and around the width of the panel. Longitudinal contours molded into the outer edges of the two roof sections add tension at the top of the car. The rear window is larger than that provided in the soft top for a balanced look. Overall height is only 0.39-in. greater than the soft-top MX-5. MX-5 PRHT models wear a fine chrome ring around the grille opening, bright bezels inside the headlamps and a chrome band in each door handle. A white-lens CHMSL is another - more - distinctive touch.