As a general rule, use less chips than cubes to obtain the same level of oaky-ness (it's a surface area thing). 1-2oz should get you where you want to go flavor-wise, but this will take shorter to get there than cubes. A good practice is to check the flavor often after about 3 days of soaking. When the flavor is *just* too much more than you want it, pull the oak and package. I say "too much" because oak flavor will fade with time.
~~ Malted barley wants to become beer. ~~