Hi, I have 130mm wide sweet chestnut T&G boards to fix vertically on the front of my summerhouse I've built. I have double battens behind with Tyvek so that's all good. My question is, due to the width of boards, and chestnut being a hardwood I've read I should use 2 fixings through the face. I was originally hoping I could secret fix them through the tongue but that doesn't seem strong enough considering the board width. I'm ok using face fixings if I have to. I know I need to use stainless steel fixings (due to tannins in the wood) and I'm curious if anybody has done something similiar and if so what were the type of fixings you used? I originally thought about nails but am now thinking a screw with a featured head (like starshape head) would be good. Maybe something like this https://www.silvatimber.co.uk/countersunk-stainless-steel-cladding-screws but doesn't have to be countersunk (if it would sink well into sweet chestnut?). Any tips or pointers? Thanks.