[Diabolical Artificer]

One thing not mentioned is how much capacitance you need to provide X current so there's no sag, which is AFAIK is 1000u per 1A roughly, so 200u for your 300mA expected is about right.

I wouldn't worry too much Andy, just get it built but leave yourself some wiggle room if poss EG, not wrapping wires round posts and tags so things can be easily changed later.

Keep up the good work, tother Andy.