Executive Summary
FIPS is an unusually well-specified protocol for alpha software. The cryptographic foundations are sound (Noise framework, secp256k1, ChaCha20-Poly1305 — all battle-tested primitives, no novel crypto). The layered encryption model (hop-by-hop IK + end-to-end XK) is correctly designed and mirrors proven architectures (WireGuard, Lightning, Tor).
The vulnerabilities I've found are primarily in the routing and mesh self-organization layer, which is where novel protocol design lives. The IPv6 adapter, despite your instinct, is actually the least concerning component — it's a thin shim with a well-constrained attack surface. The real risks are in spanning tree manipulation, bloom filter poisoning, and metadata leakage.