Anyone know what I should use to fill the gaps in the wood countertop I have. It is made of 4" Ipe boards and the gaps were originally filled with wood filler, but now are cracking due to expansion and contraction of the boards. I'm looking for suggestions on a stainable substance that would hold up to the movement of the boards throughout the season. Also any thought on what I should put on it to finish it would be helpful as well. Thanks in advance.