Propulsion is not based on %'s?While that works for non-propulsion components like weapons, shields and cargo, it doesn't work so well for propulsion, which is based on Hull volume.
I set an approximate hull, fill it with what I need, and then increase hull size until it fits... or dump stuff that I don't really need to make tonnage. Either way, using any sort of spreadsheet for that makes it easy. For mine, I wanted a tab for each step in the HG flowchart so I don't have to scroll TOO far down the page.
Maneuver is all %
Reaction is all %
Jump is a mix of % and Fixed.
(as per page 16 of highguard update)
You want J2, M2? That is 5fixed dtons + 7%
Power is a little more complicated, but, is 10% power required based on total volume. So, this needs working the ratio of power per dton ie TL8 Fusion TL 8 is 10 power = 1% to cover needs, while Fusion TL 15 needs .5% Chemical is 5 power = 2% per jump etc.,
All calculable percentages.
Fuel etc., is all percentages when worked out, based upon wanted performance.
So, pick your wanted performance, pick your wanted fixed space and % based mission items, that would tell you your hull requirements.