256 still underbid by ~16 bytes (721 lovelace) on the same
preprod_test2 governor mint shape that 128 missed by 144 bytes.
The actual CBOR delta between the unsigned tx (def-length witness
set arrays, no vkey witness, no redeemer expansion) and the signed
tx (indef-length flips, vkey witness, finalized redeemer) is
~270 bytes for this shape, not the 144 the first FeeTooSmallUTxO
suggested.
512 gives plenty of headroom — worst-case ~22k lovelace overestimate
which is trivial. For multi-sig flows with N vkey witnesses, this
needs revisiting; plutus_mint's only signer today is the wallet's
own payment key so a single-vkey budget is correct.
Kayos
fbc4955c1d