The only other way I was able to figure this out was to add components equaling the tonnage of the required jump drive, then removing those components and replacing them with the jump drive.
That's what I do. It's not that hard, and if you're off a little due to crew sizes you can make it up with fuel.
I would rather do the required math before.
I'm a math geek, and this is more math than I want to do
If you
really want to do the math, then Steve has told you almost enough for you to figure the formula (which is actually better called an algorithm, since it appears he puts armor on one layer at a time) out yourself, and you can get the remaining information by doing an experiment. You need to figure out two constants:
1) The volume taken up by 1HS (this will let you figure out R for a ship, and from R you can get surface area A)
2) How many HS of armor it takes to put 1 level of armor on a fixed area.
So simply make a ship that's 100 HS big (actually that has 100HS of internal components) and see how much armor it has, then make one 400 HS and see how much armor this has. This gives you two data points for determining the two unknowns and Bob's your uncle.
Like I said, though, it's easier to just let the computer do it for you with dummy components, since each layer will require a new calculation depending on the previous layer.
BTW, you shouldn't try to design ships until you've researched TN theory - a lot of the components you'll need don't show up at the beginning of a conventional start, IIRC.
And in answer to your other question, "yes, most of my games are conventional starts w/o instant-tech". If you're going to do a conventional start, though, you're better off bumping up your population (I start with 1 billion, but will probably go to 2 billion in the future) and HW minerals by a factor of several.
John