determining Brace Height

[Mjl834]

I'm wondering how professional and amature bowyers determine the brace height for their bows.  Are there standard brace height measurements that are used for the various lengths and styles of bows for example a 70" longbow or a 64" recurve? Many bowyers suggest a range for example 7.5-8.5 inches. How do they come up with those numbers? I've looked around on the internet and have come across a blog post on Lancaster Archry site that has a chart for recurves.

     

And another article on 3Rivers site that says modern longbows are braced at 7" and recurves 7-9".

I'm relatively new to archery and am curious.

Thanks

[Wolftrail]

ooopppss another post