Traditional recipes don't seem to aim for goo, and most of the ones you can buy aren't gooey (UK, limited sample of sources). You can try increasing the quantity of spiced, sugared butter but you may be better off adapting that aspect of another recipe that is supposed to be gooey. You ought to be able to find a cinnamon roll recipe (for example) that states it has such a filling, but swap the cinnamon in the filling for mixed spice.
From my limited experience making them, adjusting the cooking time/temperature won't help - you still want even the middle ones to be cooked through.