Hi mate, hope I can be of some help - as far as I know, although there are bows up to 84" (or thereabouts) on the Mary Rose, the average is around 77". The longer the bow, the less stress the limbs are under. If you wanted a monster bow (something 160lbs +) going to around 82 - 84" is a safe bet, as you're giving the bow the best chance of surviving.
It also comes down to the individual archer's draw length. If you have a draw of around 33" (like Glennan Carnie for instance) then making a bow a few inches longer can help.
I'm currently finishing up a 130lb self yew warbow which was 83.5" long to begin with. I cut the nocks as close to the tips as possible, and long-string tillered it like that. The plan was to then chop 1 inch off each end, then fit the horn nock and end up with a bow around 78 - 80" nock to nock. It actually broke during tillering and forced me to cut it slightly shorter than planned so I'll just have to put the nock slots closer to the tips than I usually do to get the same length.
One particular bowyer in the UK makes all his Mary Rose replicas around 82 - 84" long just for the safety of the bow and longevity of performance.
It's also really hard to come across perfect yew staves 84" long, so generally speaking if you happen to have one - use it all! If you're making a laminated warbow, go for the best length to suit draw length and performance which is usually somewhere between 75 and 80" long.
