Why doesn't your ship design screen info match your technology?
This is rather pointless to complain about since the game's been out for a long time and I'm sure others have said it before, but designing ships is hard because you can't tell what it will actually be like until it's built.
The obvious problem is with range and speed. You have a base level of technology that adds to range and speed but the ship design screen doesn't reflect that. So often I think I should add engines because going from 1 to 2 is twice as fast, except in my current game a ship moves 9 spaces without adding engines so I rarely need engines at all. Same with range, I have more than I think I do.
Also it's hard to design for defense. I try to give my big ships enough defense to survive one round against an enemy fleet, so I add up the hit points and defense to be slightly higher then the fleet's attack, but when I design a ship with 20 hp it's actually 35 when built. Of course there's random factors and starbase bonuses etc. that I can't account for when designing, but it's better than having no plan at all and just throwing stuff in.
I'm assuming this isn't something that's modable or it would have been done already. The only solution is to keep notes on paper and use a calculator to know what the ship with actually be like when it's done.