DimensionsThe dimensions given for each hull type (length/diameter) are actually quite problematic. While the cost for an initial, empty ship hull is simply linear (50,000 credits times the hull size at a Class I center, etc.), what you're getting in terms of space and material is much greater than a linear progression. Noting that the dimensions themselves are increasing faster than linear (length 30, 50, 75, 100, 130, etc.), then the increase in surface area works out to be about a cube, while the increase in volume is actually a 4th-degree polynomial. (Least-squares power regression is about 70×h^2.7 for surface area, or 30×h^4.0 for volume.)
What this means is: While you're paying 20 times the cost for a battleship hull over a fighter, you're actually getting over 3,000 times as much material for that payment. That just doesn't seem remotely right. (Fighter hull size 1, surface order 10×2 = 20 m^2; versus battleship hull size 20, surface order 600×100 = 60,000 m^2.) And that's not even considering the possibility of thicker hull-armor for the battleship.
In the past, I made an attempt to rectify this by basing the cost for an empty hull on the surface area from that chart, instead of simply a multiplier times hull size. But other considerations argue against that idea: (1) it's just really complicated and winds up outstripping all other costs in the ship construction; (2) the value you get per hull size in the boardgame is pretty close to linear in terms of weapons capacity (CB p. 18), defensive hull points (see here), etc.; (3) the Campaign Book pictorial schematics actually show a linear increase in dimensions, contradicting this table (exactly 2 boxes length per hull size; see p. 6-7); and (4) the official Star Frontiers miniatures show an even smaller difference in dimensions (for example, the UPF battleship miniature is only about twice as long as a frigate, not 4 times by hull size, nor 6 times by the table above, etc.; see here).
So I would want to fix the length/diameter dimensions given in that table above to better synch up with the cost, hull points, weapons systems, miniature designs, etc., found elsewhere in the Star Frontiers: Knight Hawks game. Something like a linear increase in surface area or thereabouts (finding this is left as an exercise to the reader). This would affect the space used on deck layout maps, especially for the larger ship sizes (no more battleships with onboard malls, parks, zoos, Olympic-sized swimming pools, etc.)
EnginesNote that the number of engines given in the "Hull Specification Chart" vary both up and down as hull size goes up (they do not, as might be expected, monotonically increase). This might make sense when you consider that there are 3 engine size categories in the game (A, B, C); it would be reasonable for the number of engines to possibly go down at the point where you bump up to a larger engine size category. Except: They don't actually do that; the points where the engine number goes down don't synch up with the engine size class switchovers. Possibly this was some kind of typo or holdover from an early draft of the game before engine sizes were finalized?
Below I've presented an annotated table with the engine numbers associated with what size the engines are (see Campaign Book p. 12), example of vessel in that category, and a recommendation for adjusting a few values so the table makes more sense. For example, for hull size 5 and 6 -- frigates and destroyers -- the number of engines could be reduced from 3 (as shown in deck schematics p. 23) to 2, or even 1 (as shown in SFKH official UPF miniatures). Here I've chosen to split the difference and set those numbers at 2 engines apiece -- you have to be careful here, because engine expense is actually the greatest single cost in the spaceship construction rules (e.g., reducing destroyer engines from 3 to 2 likewise reduces overall cost from approximately 3 million to 2 million credits). Consider also that at hull size 4, the text for the pirate Corvette stipulates that it indeed has 2 atomic engines for maneuvering (SFKH0, Warriors of White Light, p. 13). For ship abbreviation codes, see here. You could edit some other places in that chart to taste, but I think this is the bare minimum to rationalize things.