Number of springs is like number of sugars in coffee IMHO - whatever suits you. I use 4 in Strats and Marvins, Bill Callaham insists that having 5 is mandatory, Clapton puts a wooden block in to hold it 'locked' because he can (yes, it does relate to springs because if he didn't want any there he could simply use a hardtail Strat!) and probably because 'its always been that way' and 'common practice - the right thing to do' most players reduce the number to 3 without bothering to 'test' the feel with different setups. And of course, we should remember that the original designers of the Strat put 5 there because for some reason they wanted to and they could!
Just by the way - what is the standard 'pull' on springs supplied with a Fender Strat? Anyone bothered to measure them? Doesn't necessarily follow that all springs have the same force, cheaper ones may well be a lot less than genuine Fender USA for reasons of economy.
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