I’m really curious about how you are going to mount this to that little bike. Have you watched any of Koen’s videos?
What Dave mentioned about the nozzle. You may have not had time to look all through the forum. You should look at the nozzle Bryan White made.
Also the fluted nozzles that KristijanL developed.
I have made both of these for the simple fire I built. Haven’t been able to test them yet but they are proven designs. This is the Fluted nozzle in my SF.
This is a close 3/4" nipple welded into a 1" elbow with a 1 1/4" pipe cap welded on it. I just started out with 1/4" holes and will fine tune from there.
Either of these will screw into the fitting your existing nozzle is it and can be easily interchanged.