in general, expect a "heavier" presence. more "oaky", toasty -perhaps a bit of char roast, quite carmelly. I have had good success blending heavy with medium toast. heavy on it's own is not quite my thing (when used at equal doses as lighter toasts). I like oak to complement and not dominate. that being said, you could use strictly heavy toast, just perhaps scaled back a bit more than you would dose with say house, or medium toast.