Hi Richard, I've just measured it and looks more like 1.65m long and 1.2m wide as best I can tell.
I'm guessing the casing may be 1.8m prior to filling and elastics being fitted, and it pulls in a bit shorter when fully lofted.
It leaves feet and head uninsulated so probably would describe as 3/4 length as you say.
Does that still suit ?
Cheers, Paul