personally i'd go with the mark VI. based on how far you've gotten with the helmets, the somewhat tougher mark VI would be a good match. plus the mark v from reach looks very small and doesn't cover much, so you'd have to devote a lot of time to an underskin. the mark VI is a bit bigger and covers a larger area which makes it easier when making the rest of the armor. plus the detailing on the mark 6 is easier. mark 5 theres some bits and pieces that are hard to include in detailing the armor