My best guess is 50 35 10 5. Maybe 51 41 4 4. Something in that range.
It could be radically different though is we knew more about what each person had at risk. For example, are any taking less or no salary?
I would say: 57 37 5 1 potentially seems appropriate to me.
A and B having real money at risk get the lion's share and everyone gets some credit proportional to the time they have volunteered to get the thing going.
While it is all still on paper, you might also want to work out who's pot future stock incentives come out of. Is it A only or A and B equally or proportionately? Alternatively, do you carve out a block now for such purposes perhaps based on all 4 contributing proportionately to the block.