b31 alternator fine tuning

[EDDIE SIMPSON]

hello. i m a bit confused by bsa service sheet 312 carb settings. my large fin 350 has 1" port and 376 carb , needl;e 3rd notch ,260 main jet and bellmouth.
it runs ok with a goldie silencer . should i go for a larger main jet? after a run the engine is hot  but i am running in. the issue will be when  i will need to hop along the odd motorway junction at a steady 60 to 70mph. do not want to seize the engine.
any advice?