Back when I had a 44 mm carb I used this jetting
125p
155m
2.0 n/s
shiny silver spring ( think it was around 16- 18 psi pop off
That should be a good starting point.
water routing -
I run one cooling line from the pump with a "Y" feeding both fittings on the bottom of the exhaust manifold - the 2 fittings on the head each have their own overboard pissers
The other pump cooling line feeds the bottom fitting of pipe - From the upper pipe fitting a line is run to another pisser with a "T" in- line to feed the stinger. I reduced the stinger line to a fuel line ( whatever that diameter is). Engine gets cold water and pipe gets its own.
I run my 2 superjets the same way but with a flow valve feeding the stinger - Don't know if there is any real benefit of the pipe having its own dedicated cold water supply but works well for me.
I made a flush rig with 2, 1/8 nipples that fit into the pisser holes and reverse flush - I flush the 2 head pissers without running the motor then the pipe pisser running.
Pay close attention to mounting the pipe - nothing should bind when you tighten things up -Use generous amounts of C5A anti seize..... My pipe has been on that motor for over 6 years and has never come apart.
The bastard red pipe is really not a bad pipe for the money.
Throw a 48mm carb, head, enhancer, reeds, bore the nozzle out a few mm's (85mm comes to mind - been awhile) and she should be a nice hard hitting ski.