You can try linear scale, this one is quite simple.
Exemple Em:
e------12--14--15--------
b------12--13--15--------
g--11--12--14------------
d------12--14------------
a------12--14--15--------
e------12--14--15--------
it's just a few notes added to petatonic. To see (hear?) how you can use it just listen to Thin Lizzy's or Metallica's solo to Whisky in th jar. (Although Metallinca might have this solo in different key???)
There is only one god, and his name is Jimi Hendrix.