Scooterotica

not a dial in power jet, but I run Mikuni TM38 with standard Mikuni power Jet (and its not expensive !!).

Works really well for me.
Great fuel consumption when riding with everyone else elc (unless opened up)
Nice and easy for pottering around town etc
Can feel powerjet kick in when opened up

Never really thought before about positioning of power jet nozzle compared to slide, but guess that makes sense.
Also on this carb there is a positioning hole etc for the power jet, so Mikuni designed it to be in this position.

Thanks for the image, which shows that there is some deviation in manufacturer's tube lengths but the vertical orientation is the same.

Ta