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I guess the easiest way to check dimensions and shapes is have a look at Skate samples site and go off those ones.
Eg, the 8.75 board on there has a long wheelbase and length, compared to DLX or especially the Black Label board, although not by a lot, it is still different.
Having had some of the Sci Fi boards in my hand, they are the generic shapes, same as the BL 8.5 board, but the 8.75 is different.
I didn't compare or check the 8.25, but the 8.38 board (Omar special shape) is definitely different - BL board is way longer when compared the two which I have both had.
More than anything it is just the boards I have had or currently have, more so in 8.38, 8.5 and 8.75 sizes, but I have also had a number of 8.25 boards come through my hands, with some being different here and there in dimensions and shape, although nothing I recall stands out particularly that any were this or that, only that the DLX 8.25 of which I have lots and skate some has always been bigger than almost every other 8.25 board on the market, again not by much, but when lined up standing on their side, the DLX 8.25 stands up a mm or sometimes two above the others in the side rail.