You have a good question there, Buger. I am not a bowyer, but I read your question and thought it might work. You would have to try it and see.
I know that there are composite bows that have a core of wood, a belly of horn (compressible, stores energy when compressed) and a back of sinew (stretchable, stores energy when stretched). But the belly and back are glued tightly to the wood so that they WILL compress and stretch when you draw the bow. Otherwise they would just slide along the wood and not do any good.
It might be that extra sticks tied to your weak bow, would suffer from the same problem. You might need to glue the extra wood to your bow. But it seems that if you are going to go to all that trouble, and unless you just want to try it to see if (and how well) it works, it would be simpler just to take the lessons you learned from this bow, and make a better bow.
Wow, lot of advice from somebody that doesn't really know what he's talking about...