the rocker cover bolts don't need to be tight at all, what i do is use a long extension with the 10mm socket on and hand tighten them all in a sequence from left to right doing opposites ( left then right then left etc ), then fit the ratchet and just give them a quarter of a turn. it doesn't take much to displace the gasket so don't go too tight. check for leaks after and tighten or loosen if required.