Weighting Big Boards

I have some big boards I made a few seasons ago. They are the triple board type. I've been happy with them, but after this weekend I think I need to weigh them down to get more pull from them. Anyone have any advice on what to use to weigh them down? I want to evenly distribute the weight across the three boards. How much weight do think per board? I would love to expirement with multiple weights but can't spend a fortune on weights trying to dial them in. Thanks for any advice.