I have a new tufnol spacer. holding it against the flange with fingers, then holding it up against the cruel light of day, I can see a little bit of light peeking through in the mid portion. May be up to 0.25 mm at most would be my estimate. So flanges are slightly bent towards the manifold.
So do I wet and dry sand on glass ? what grit is sensible ?
then as I have no O ring groove do I use a paper gasket instead ( so it'll be a paper gasket tufnol sandwich)