Hi, I'm experiencing some issues with my macarons in that all those cooked on silpats have a large air pocket/come out hollow. I've tested by making a batch and baking half on parchment paper and half on silpat, both at the same length of time and same temperature and those on parchment were nice and fluffy inside (a bit brown on top but that's another issue!) Does anyone know what could be causing this? Do I maybe need to adjust the baking time? I use french meringue method and am baking in a conventional (no fan) oven at 160C for 16 minutes. I know I can use parchment paper and then place a tray on top to shield from the heat and avoid browning but I'd like for it to work on both, especially as they always look more uniform when using a silpat. Any help appreciated!