I think that might be too much vanilla.
remember, most of vanilla flavor comes from the aroma, and its EASY to overpower.
you an always add more, but can't take any out without blending the beer with another non-vanilla'd stout.
So I'd taste before bottling. In fact I'd chill the sample to serving temp, then taste and smell, and add more vanilla at bottling if needed.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10