Hi Peter,
Thanks for taking the time to understand the proposal and give thoughtful feedback.
With this kind of "static" approach I think there are fundamental limitations because
the user has to commit "up front" how large the CPFP later will have to be. 1kvB
is an arbitrary value that is two orders of magnitude less than the possible package
size, and allows fairly flexible amounts of inputs(~14 taproot inputs IIRC?) to effectuate a CPFP.
I'd like something much more flexible, but we're barely at whiteboard stage for alternatives and
they probably require more fundamental work. So within these limits, we have to pick some number,
and it'll have tradeoffs.
When I think of "pinning potential", I consider not only the parent size, and not
only the maximum child size, but also the "honest" child size. If the honest
user does relatively poor utxo management, or the commitment transaction
is of very high value(e.g., lots of high value HTLCs), the pin is essentially zero.
If the honest user ever only have one utxo, then the "max pin" is effective indeed.
> Alice would have had to pay a 2.6x higher fee than
expected.
I think that's an acceptable worst case starting point, versus the status quo which is ~500-1000x+.
Not great, not terrible.
Cheers,
Greg