Andre,

I think my 1/8" Phil was 7.4mm wide overall, the tooth is 3mm (going from memory). That puts the chainline from shoulder at 5.9. 1/8" EAI is 6.73 according to Mr. "Interchangeabilitude" Sheldon.
I could be a little off, I have a crappy caliper.
Anyway, I think you could easily get a spacer in there and still have enough thread for a lockring; though that may not be ideal for you.
With me, my goal is to have 14 thru 17 tooth Phil cogs so I can get a full range of geraring (91 - 75 G.I.). I may even get a 13t...