What is the stock speaker mounting depth in a 03 wrx? I've searched but haven't found any relevant results.

i'm trying to make spacers for focal 165As. they have a 66.2 mm mounting depth (about 2.6"). i need to know how thick to make the spacers. i'll just take the stock speaker mounting depth and subtract that from 2.6, and then make the spacers that wide. does that sound like it would work?

also, what is the best type of wood to use for custom speaker spacer rings?