I was thinking of doing something like the drawing of splitting the pipes you've done(but it would have been integral to the block top), but I'd have had the inner carry through and the outer vent from a barb next to the inlet, I gave up cause it'd been to 'tall' once I'd allowed enough distance for the flow from the 8 outlets(4 for all intents, cause each two are joined) to 'equalise', because the outlet would still be offset...
BBs going to use the entire diametre of the block as his outlet 'barb' I think, or that was the impression I got...
I like the idea of doing it small as a fitting!, that's excellent
, I'd have both barbs on the same side you have the 'outertube' outlet, to do away with any 90Deg bends.
*EDIT* You beat me to it!
... I'm going to have to work out how my scanner works!, I like that '
on the fly' look as well
...