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Yeah RG979s
From what I understand, the problem isn't the length of the nut but the thickness of it. A longer nut won't fit in because the mudguard braze-on gets in the way, but if the bolt was longer then (as it's thinner) it would work.
If the TRPs only come with a short bolt on the front (like a normal rear caliper) then I think the only solution is a different caliper choice; probably VO Grand Cru.
RG957s? I've had no issue with those TRP brakes even with a carbon fork. Anyways the thingy they screw into are available in all sorts of lengths dependent on the distance front to rear of the fork brake mount.