Going back to titanium - you seem to be comfortable with how you're using the material and you're taking precautions - great. But you didn't mention this when you first brought up titanium and I think it's incumbent upon us, if we're making recommendations, to give the appropriate background risks (if they exist), especially if we know what those risks are.
And here, I really believe there are risks. I would never use titanium fasteners for a suspension joint - too much risk for me. Again, you seem to know your stuff and you're happy with what you're doing. For someone who doesn't understand the risks I think it's on you to give the full story if you're going to throw that out there. I personally don't have a clue what loads were factored in when my suspension was designed and whether any off-nominal use cases were factored in, such as curbing a wheel at 20G. I'm going to use the strongest bolt I can get (within reason) and for me, that's the alloy steel bolts offered by McMaster just about every time, having considered all the cost, quality, availability, etc implications. Again, your priorities probably differ from mine. Just throwing this out, but I'm guessing most other builders will tend to be closer to my list of priorities and have less subject matter knowledge (or care to run down the rabbit hole).
I haven't done the research to see what's available with respect to pricing for A286, Monel, or titanium aerospace spec and sourced fasteners so you've got me there. I have no idea how they truly compare cost-wise to what's available from places like McMaster and Fastenal. You didn't originally mention that you were able to source your fasteners several years ago when these were on the cheap; but you did suggest going onto eBay to find some with the only caveat being to watch the grip length. Nothing about what steps one should take to ensure what's being sourced on eBay is legitimate stuff - should we contact the seller and review their certs before bidding? How do we verify that their certs are legitimate and not printed on someone's personal computer? What chemistry bounds should we be referencing when verifying a lot is metallurgically correct, and that the correct heat treat was used. In your reference to A286 you don't mention what heat treats should be sought after and which should be avoided.
Here are 2 sources for A286 fasteners, both seemingly legit (I just did a search for A286 bolts and picked the first 2):
Delta fastener
Extreme fastener
If I were someone who didn't know anything other than it's a good idea to use A286 whenever I can, which of these companies and which spec should I purchase? Someone not well versed at reviewing this type of information may not know and decide to go with the lower grade material, I mean - it's A286 right? So ... should I use a 130ksi A286 bolt which has great oxidation resistance at 1300F, or should I use a zinc plated alloy steel bolt rated to 170ksi for my upper control arm attachment point? The safest solution in this case, and probably in 99% of other searches regarding "which bolt should I use for my suspension", is to go with the 170ksi commonly available alloy steel bolt - no further explanation or rabbit hole digging needed.
Fundamentally, I don't think we disagree Neil - we should use the best stuff we can afford. Our philosophy on what makes a good design perhaps differs since our priorities aren't in alignment - and that's alright.
But take a step back and put yourself in the shoes of a novice builder looking for information on what bolts he should use for his car. Do you believe suggesting A286, titanium, and Monel fasteners is a good idea without also including all the other factors (risks, cost, availability, material strength differences)? Someone coming along a few months from now and who digs this post up and sees that you're making those recommendations may not know to dig into the rabbit hole to figure all this stuff out. So I think it's on us as subject matter experts (and I use that term very loosely in reference to myself) that we provide the appropriate background information - especially if we're going to make recommendations that carry significant risks (IMHO, you may not believe those risks exist and that's why you didn't feel it necessary to include all this extra "stuff").
You have very pretty bolts. It's a whole 'other loaded discussion on why one would choose to use a 12-point head over a 6 point head and male vs female hex. While I appreciate your anecdotes and experiences I think you should also pepper your posts with the appropriate background info if you're going to make recommendations to pursue non-traditional design options - I include the use of A286, titanium, and Monel fasteners over grade 8+ alloy steel as a non-traditional design choice. At least, I assumed you were recommending the use of A286 whenever possible since you threw it out there.
(phew, end!)