in order to justify a 40ft leeward hull you need a much smaller windward hull
I think 40ft might be tight, but there can be some savings in the WW hull

If you had athwartship doubles, and a queen size is 1.53 m
I think the ends look like taking 2.4m
a sensible (or tolerable) liveaboard width might be what, 5.m
but you have to steal some above the bunks to secure the glazing sides, 4.6m ?
thats a 10m hull

so in the hull between cabins you have remaining 4.6m
an easy 1m each side; 2.5m remains, is that enough for a water closet and shower?