It depends upon your actual goal. Do you want to glue up some lams, and a backing, and hopefully get a perfectly tillered bow?
Do you want to glue up a blank that is ready to floor tiller?
The first approach is usually employed by fibre glass bowmakers, though some all wood bowyers do the same method successfully.
They usually develop the right combination by trial an error. I don't have much experience with that side of things. From memory I think they use a taper of 0.001" , 0.002",0.003" /inch.
You could try a 1/8" backing, core 3/16", and use your lams as the belly.
Keep in mind you may need to add a power lam or riser to thicker up the handle area, depending upon the style of bow you are after.