By the way, it's a very good idea to divide the backup in such a way, that no one can use it if somehow it is found. I will definitely fix this point soon.
The most proper way to do this is with
Shamir Secret Sharing Scheme. For example, you can choose to split your money into 5 seed phrases, 3 of which are enough to recover the money, and hide them all in different places. This is better than Multi-Sig, because you don't need every seed's master public key.
In any case, don't divide the seed phrase in multiple parts, you're most likely going to lose money.