I don't think anyone tried it before, but Cable43 has the GTSpec rear STB...He got the sedan rear STB by mistake and said it was totally different.
<img src="http://corksport.com/store/image/iw9m/99p-suspension_misc_/GT_SPEC_Strut_Bar_-Rear_Sedan.jpg"
Looks as though you have some sheetmetal inbetween the strut towers (the Protege5's have just plastic panels that are in the way of the towers, that would need to be cut). If there's a way to cut some of that metal out to allow the bar to run across, maybe...(I never saw the trunk of a sedan, so I'm just guessing). The strut bolts on the top is the same in both sedans and wagons...So the bracket fits, but I can't tell what's in the way.
Does anyone have pictures of a sedan trunk without the plastic panels? Maybe we can find out.
WiL