I need to install a 30 mins internal fire check door with a new frame, and am wondering what the minimum doorstop size needs to be in the frame. I have purchased a ready made frame which has 13mm doorstop, and I am planning to router the frame to fit the intumescent fire/smoke strips. Do I still need to upgrade the doorstop to 25mm? Since the new firecheck door needs to be painted, is there a requirement in the use of fire-resistant paint? many thanks in advance.