don't know what to say...
first, great work on the sideview, i understand completely.
second, it sins totally against rotor and billA's views. personally i do'nt have too much xperience with making blox; but, the first and only block i have ever made is based on xactly the design you just drew. sad to admit that the performance of such a block is rather disapointing (+/- same as maze2). there should be alot more to gain out of the dual outlet design.
try look at it this way; u r not trying to equalize flow velocity troughout the whole block. high flow velocity at inlet/chip area; low flow velocity(=low flow resistance) at the outlets.
so as your gut feeling would tell u to use 3/8 for outlets and 1/2 for inlet; better doing it the other way around...
i'm gonna try get you a sideview asap (killed my acad install )