On my
head that I can see now, my flush is t'd between the rear of the head (electric box side) and the bottom of my b pipe (by the manifold)
I've got an exit cooling line from front of head to one pisser.
The fitting on top of the b pipe in the diagram you posted:
I've got a cooling line that goes straight from that fitting to the front of the chamber, (by the gas tank)(not to the head), which is t'd to my second pisser.
I'm pretty sure that it's inline flushing and not back flushing but it's always worked for me. My friends got a stock ski that's flush is set up as Herman,s.
There was a thread re back-flushing not that long ago, I think posted by Yamaslut. NOTE::: MINE's::: A STOCK HEAD WITH B PIPE