canvas 90 or 88

can anyone help me identify a canvas that came with a project lightweight ive just bought. the front is definately for a 90,but the sides measure 53 inches long which would make it fit an 88 ,i think. its got the holes in the sides for aerials, making it military, but theres no makers mark on it, so i rekon its for an 88 with a 90 screen conversion. handy if someone could measure thei 90 sides and let me know.
cheers, loz...