After that will require going to a braided line? There are some options here:
A) Fit an extra bottle and run 2 5mm nylon pipes. (recommended)
B) Fit a Y piece at both the bottle outlet and Pulsoid inlet.
C) Fit the larger braided hose.
I mention option A as the best because it carries both the advantages of having the nylon pipe AND a lower pressure drop during use from the extra bottle.
What is recommended for up to 200 HP for about a 3 foot run?The 5mm nylon pipe should JUST make that. A symptom of reaching the pipe's flow limits is generally an overly rich mixture regardless of the size of the nitrous jet.
If we keep it to 3 feet, the nylon will support 150 HP?Yes.