Thank you all for your responses and insights. Really appreciated.
I will try via PC plat CS HI Montmarte since it appears they are the only ones that can fit four or more to a room and possibly for the least amount of points; 30K. Failing that I will go with either the only HIX in town and send the hotel an email so that both rooms are next to each other and/or via a connecting door or go with the CP Paris Republic which is steep on points but if they can upgrade me to a double bed room then that may work out.
HI Gare De L'est does not appear to fit more than 3 to a room as an option online on a paid stay.
Once again thanks all!