Automatically assign override-values

[Sami Huhtala]

Hi,

I'm a bit unhappy with Lilypond's default ties and working on an idea to 
fix them. Is it possible to automatically assign override-values to a 
tie based on it's length? (e.g. if tie is short, say less than 5.0, to 
use certain 'x-gap -value).

Sami