BKDee

Hi, My tank maker has just delivered my custom tank and solid wood cabinet to me. It’s a 150x75x60. What can I do to fix this 3mm gap on the right side of the tank? The tank maker is asking me to add another 1cm foam on top of the 1cm black foam I have. Anyone have experience whether that will be safe? I’m really worried the tank will crack in long run. I read mixed suggestions from other reef forum. Some asks to add another plywood on top and add shims in between the wood and the stand surface… Any other easier DIY suggestions?