I've only made a mousse twice before and used the recommended amount of water. Tbh i found them a bit "firm" for my taste so next time will have to experiment with either a bit more water or a bit less MAM.
I think to use 250ml might be a bit toooooo much? Have no idea though, just guessing
i use 200.. well i dont.. i just put water in.. even with my shakes.. i never measure anything.. i think i got used to doing it.. and dont measure anymore.. so yeah.. i use 200.. hehe