amount of chocolate extract per batch?

am brewing a PM sweet stout that has a pound of chocolate malt as a good part of the specialty grain. was thinking of splitting the batch and making half as normal and half with added chocolate extract. I have a 2 oz bottle of Nielson-Massey Chocolate extract and was wondering if I should use the 2 oz in the 2.5 gallons or should I use less? I like the stout as is and would like to make a "double Chocolate" stout which has a good chocolaty taste but not overpowering. Also with adding the chocolate should a little lactose be added to sweeten the chocolate some? I have read some of the chocolate threads and this has actually raised this question as originally I was going to use all 2 oz but am wondering if this would be too much chocolate in 2.5 gallons. any info and insight/suggestions would be appreciated.
TIA
Ben

2 ounces is about what I like in 5 gallons. I would start with1 ounce.

after reading here I thought 1 oz. Thanks. also acouple of other questions. when to add it? to primary fermentation, secondary it or add to the bottling bucket?

UnderThePorchBrewing said:

after reading here I thought 1 oz. Thanks. also acouple of other questions. when to add it? to primary fermentation, secondary it or add to the bottling bucket?

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Bottling bucket and taste just to be sure before you bottle.