I wonder about the decreased roof structure, if it's just replacing a sheet of steel then it might be heavier?
But if it's replacing a structural member above the driver's head then it needs reinforced elsewhere, no?
Some had T tops. Not sure what years exactly early on, but the early Fox years had them. The only years T-tops were available in the 1987-93 era were 1987 and 1988.
Among changes in the second model year, the 1975 Ghia hardtop model added a flip-up glass "moonroof" option ($422).
One other bit of '76 news involved the Ghia moonroof, which was now optional for other models and with either silver or brown tint.
I know even the SN95 & New Edge models you could get a sunroof as a dealer option.
I had a T-top in a 1978 Mustang. It leaked but I still loved it. Ford and most of the other automakers quit making convertibles for a number of years for safety reasons. I had a new 1994 Mustang. I don't believe a sunroof was available in it.