Josh,
To clarify, you have a VERY BAD DESIGN.
Part of the reason so many other Teams persist with such bad designs is "because Racecar". I have heard too many FSAE students say "But it's supposed to fail like that, because it's a racecar...". Yes, literally!
But the main reason for your bad design is that you are simply copying everyone else. If this is not so, then please provide a comparison of above design against another ~half-dozen obvious alternatives, with OBJECTIVE NUMBERS for cost, strength, stiffness, lifetime, etc.
Anyway, here are some aspects of the design that are crucifiable offences (my dear old dad would have nailed me to the wall if I suggested them ). Worst offender first, then in no particular order:
1. COST - You start with two ma$$ive billets of expen$ive alloy (upright + axle), then machine away almost all of them! The end result is a flimsy upright/wheel-hub assembly that, despite still being overweight, would quickly fatigue fail from the stress raisers you put in it (Goost's #6, at the highest stress-reversing area of the axle!). Except that the wheels will be flopping around so much that you won't be able to drive the car hard enough for the loads/cycles to do their work (see why below).
In short, a very expensive way of building heavy and weak parts, which are also perhaps the most crucial parts of the car! "But, hey, that's how everyone else does it!"
I most certainly would not buy a part like that. And any cost-conscious Production Engineer at any (good) company that you might work for in the future would not like it either. The profligacy you are practising here is common in the Racecar world, but NOT good elsewhere.
2. UPRIGHT - Too much material in the wrong places, and not enough in the right places. So, overweight + understrength!
How did you come to such a design? Did you have any strength/stiffness targets? (Yes, I know, cost was no issue...) More importantly, how many alternative designs did you consider? What are the numbers?
3. AXLE & BEARINGS - Just a "...light press on the spindle and a slight slip in our uprights", eh? And "...an inner race spacer to snug up against.", with the snugging-up done with an aluminium nut? And you are "...following SKF reccomendations for this [shoulder] diameter", but seem not to have noticed the word "minimum", which probably applies only to HARDENED steel axles...
I very much doubt you would get through a single 22 km Enduro with the design as shown so far, let alone any significant testing. And that is even if you use the world's most expensive aluminium alloy (the usual "racer" approach to solving such problems).
4. BRAKE DISC - Is it a good idea to drill a "speed hole" in the most highly stressed part of the disc? Or, put the other way around, where do you think the first cracks will start to appear in the disc?
5. OVERALL - You are a very-first-time Team. So why not buy one of the many small-car axle/bearing/hub units that are available off-the-shelf, in a size just right for your needs? These are much stronger and stiffer than yours, would have a lifetime of around 100,000 miles (cf. MegaDeath's ~2k miles), have a similar mass to yours (or perhaps less, after some machining?), and be much, much quicker and cheaper to get done.
If you think you can do a better job, then try next year. But compare objectively, with real numbers.
Z