To follow up with Spanky's thread....
grip depth and grip length factor into limb tiller and repeatable hand position/bowhand 'heeling'. To keep the handle length as short as possible, you need to know the grip length. You need to also to be able to make the working limbs as long as possible while keeping the limb arc correct. Factors like this are what make a truly custom bow...not just what kind of wood and glass color you want. Most bowyers work off a standard riser length for a particular bow length. They use standard grip sizes, built for the 'standard' shooter. However, we all know that all of us are different. No wonder that guys will shoot brand A well and brand B they can't hit the barn door with. In shooting both bows, it happened to work out that brand A happened to be sized and tillered for their unique characteristics, not that brand B was a bad bow. The 'standard' 68" longbow with a 16"+- handle has been around so long because it fits most people generically and most bowyers that build for a living must make bows to fit the masses or they go broke. But are we all the same? No. The sum of all the small things in a bow will add up to make a very custom bow that is built to fit that one person. To do this you must in a sense throw out the book on standardization. A bow that is built like the old self bows, tweaking and fitting to the shooter becomes a bow that doesn't get left on the bowrack very much because it's always in use. I try to take the old Hill bowmaking principles and use these to fit the bow to the particular individual's needs. Why did Hill's longbows work for him? They fit him and his needs. Schulz was taught personally by Hill yet didn't shoot the same length bows as Hill. He's about 7" shorter with shorter arms, so his bows were sized to fit him and his needs. Yet both bowyers built bows based on the same design principles. Photos of them both shooting reveal that each's bows had same limb bend, proportionate handles, etc. That's customization. That's what I'm talking about.