Eight note properties, flag style

[kpk1]

Hello, I wonder is there a way to change (globally) properties of all single 
eight notes (flags, stems).
I don't like default settings because flags are so close to the stem and in 
some cases they overlap with other elements
while used with multiple voices.
 
Also, I am having problem with style attribute. There aren't any explanations 
in documentation on how to use it.
Layout section in documentation is not so rich in details as other sections.
 
Thank you very much for your answer!