drac

I use a 6" extender on the spanner wrench and bear down on it

Also ,YS has a new flange installer tool with three pins for the male side flange . On the single pin tool the lock pin will bend and distort the flange face and cause it not to seal correctly on the header face. Sometimes because of this, it will leak and not tighten correctly.
You can resurface it with some 400 wet sandpaper if that's the problem. I don't recommend the extender on the male flange to the engine because the washer takes care of the problem with keeping it tight and sealing the face.

I recommend getting the three pin installer it`s much better. Or drill and install your own pins like I did.

Bryan