Why not 2-of-3, so you only need locations A, B and C? With this setup, 2 locations are always enough to restore your funds. With your 4 locations, having only 2 remaining locations gives a 50% chance of losing access to your funds.
Well... Look, I understand that a 2-of-3 seems better and many people advise in favour of it.
However, I don't like it because I haven't found a way to properly backup the xpubs.
For those who read this, but don't know how multisig works, you basically need all the xpubs of all the cosigners to describe the wallet, but you need part of them to sign the transaction.
So:
2-of-3 : A, B, C - You need all the xpubs and 2 of the seed phrases
2-of-2: A, A, B, B: You need all the xpubs and the 2 seed phrases.
Let's back these up.
In the 2-of-2 you need 4 backups for the seed phrases but you don't need to backup the xpubs because they can be derived from the seeds.
In the 2-of-3 you need one backup of each seed phrase and one backup of each xpub.
You could do it like this:
Location 1: Seed A, xpub B
Location 2: Seed B, xpub C
Location 3: Seed C, xpub A
You have the same redundancy, because losing one location will allow you to have the necessary pieces to unlock the wallet (all the xpubs and the 2 seeds)
But, I haven't found a good way to backup the xpubs. They are huge sentences of random characters, so one simple mistake can lead to money loss.
This is why I avoid 2-of-3.
I don't like multisig. It's not intuitive, I'd always fear I'd mess up, and it increases transaction fees.
I understand. So, without giving away your setup, what do you think is a better way to do your self-custody ?