Question about Pure Rock Slim 2 - 672760

Hello everyone! I have two questions: - Does anyone know how large the contact surface (i.e. the white surface) is? Is it at least 40x40mm wide? - Is it possible to use liquid metal based thermal grease with this cooler (e.g. https://www.digitec.ch/en/s1/product/thermal-grizzly-conductonaut-liquid-metal-73-wm-k-1-g-thermal-grease-5672233) ? In other words: Is the cooling surface (white) nickel-plated and not made of copper or aluminium? Many thanks in advance!