Hi,
 I am working on tweaking a 64" recurve design (2" wide limbs). There are 2 lam layers and 2 glass layers. As I increase/decease the pull weight, I wonder which lamination layer should be changed, or what ratio would be good to maintain between the two.  

For example: I have a .256" stack with a .070" parallel and a .100" taper (.002/1"). Glass is .043".

If I want to bump the wieght up by #5 or #10, should I add to the parallel or the taper, or both?

It really doesn't matter. As long as you don't change the taper rate per inch the result will be the same. If it is a takedown and you are using 36" tapers and the limbs are less than 36" you can increase/ decrease weight by sliding them outboard or inboard. I usually grind my tapers longer and thicker than I need so I can fine tune this way.
Bonner

I am with Dan don't think it would matter.  By grinding the taper just a bit thick you can precision adjust you stack height.

I would add to the taper a bit first, since it is .028 at tip. But I don't think it really matters either way..