I’ve only seen Skull once (at the cinema) and my rather vague recollection is “meh”.
It’s worse than you remember. Saw it for the first time in a decade about a month ago (a fanedit) and hoped I would get something out of it in spite of it’s flaws. I, too, would have given it a 6 based on memory, but I honestly think it doesn’t deserve higher than a 3.