Its not so much for hull space per say as it is for energy. Total component weight not including the core is 56 for me. But when designing when you have a predefined energy output makes it hard to get the ratios you want.

IE

I want a a ship with 1:10 attack:HP ratio. Building the ship and core first may cause my ratios to change.Or a may even run out period.

If you desging your components first, you know how much energy your components will need so you can build you core to order and the your ship.

I am rather new to this game still and looking through the guides, it seems most of the ship design guides seem to be backwards and cause cramping.

This may not be so important in building swarmers and pships due to the nature of the ships but building your big ships and you have specific ratios in mind for attk/hp ACU and ABS you would design the systems first.

IE

Design Weapon(s)
Design Special(s)
Design Computer(s)
Design Armor(s)
Design Powercore
And finally
Design Ship

Is it just me or does this seem to be the better way to go?

I just started playing in the last few days.  Upto encryption 14 missions and in the top 100.