Recommendations towards oak cubes

i have a 2 1/2 -3 gallon batch of barleywine that i want to rack either today or tomorrow... i have Hungarian medium toast oak cubes im not sure of how much i need to put in there.. (im trying to just mellow out the harshness of the alcohol while introducing some mild flavors.. if that makes sense)

i plan on aging the barleywine on the oak cubes for about 4-5 months.. (august) so all in all im not sure how much to put in there... ( 1oz, 1/2oz, ext?)

I'd put about 1/2 to 2/3 of an ounce, depending upon how dark the oak is toasted.