On reflection, I compared these to a straight 2d6 (which I transposed by subtracting 7 for purposes of comparison). I should have realized this, but graphs are easier than thinking:
d6-d6 is functionally equivalent to 2d6.
That means that in mechanical terms, Starblazer Adventures is basically Traveller with aspects. (Well, in terms of dice throws, at least.) If you’re going to ditch the Fudge dice in favor of d6’s, you might as well just transpose your ladder by 7 and eliminate the wonky math.
Also, I realize I’ve been representing 2d6 as a bell curve, which is not strictly true. It still achieves the same effect of producing more consistent results, but wrong is wrong. Whatever.
If none of this makes any sense to you, don’t worry about it.
EDIT: If you’re not familiar with anydice.com, the basic trick is to change the view from Table to Graph as soon as you get there. Makes life so much easier.