I have tried various ginger cookie recipes over the years, for gingersnaps, gingerbread cookies, pfeffernusse, and most recently pepparkakor. I never find the cookies to be spicy enough—I assume, not gingery enough. What can I do to bake a really spicy cookie? By way of prior research: I am often generous in the measures of the spices; in particular, I often put in more cloves than the recipe calls for. (And when I made candied orange peel for the first time a few years back, I thought that might be part of the solution. Once I tried adding it chopped to the gingerbread cookie recipe above, but the result was equivocal.) 
I often find that fresh ginger tends to lose its freshness over time when heated, and this might happen here.  So I suggest ginger powder.  Similar to garlic powder, this is a very fine powder made probably from the dried fruit, and surprisingly intense and close to the original.  It might be difficult to find; I buy mine at an Egyptian spice dealer.  (It's also awesome to put into hot chocolate...) In addition, you mention an extra dose of cloves.  Maybe try reducing that, as cloves tend to have a somewhat numbing effect in the mouth. 