newbie questions: stretching

[Charles Neuman]

Is stretching the high treble an art or science? That is, do you balance
the single and double octaves by whether or not it "sounds good", or do
you go by a specified amount of stretch in cents? I've heard both
opinions.

If it's more of an art, I would imagine there are those who favor the
single octaves and those that favor the double octaves. Is this the case?
Also, do performers ever specify the amount of stretch they like?

As for the bass, I'm finding that if I tune the bass notes at other than
beatless octaves, it sounds muddy and out of tune. But then I get those
horrible sounding 10ths, which I know I should expect. Any advice on
balancing these two problems?

Thanks,

Charles Neuman
Plainview, NY