As far as I know the values are somewhat arbitrary, but once implemented became relative. For example a T-Wing would have less hull than an SSD...ect. I suggest determining the type of ship you want to make such as a Capital Ship, Starfighter, or mid-range...then open one of the prototype files that has the same type to get a basis. Also, just so you know on my FotE based mud, quite some time ago I added in the ability to make and setup prototypes completly online. So it may be relative to which FotE based mud you are playing as far as how things are done.
Hope this helps, at least a little.