Specifically, the recommendation is to interleave the transactions in a way that alternates between transactions to Alice and transactions to Bob. For example, the sequence could be 1.1 to Alice, 1.2 to Bob, 1.3 to Alice, 1.4 to Bob, and so on. The purpose of this arrangement is to avoid risks associated with mempool split.

In cases where there are two transactions with the same fee of 1.1, one to Alice and one to Bob, there is a possibility that half of the nodes have the transaction to Alice in their mempools, while the other half have the transaction to Bob. This situation could potentially be exploited in replacement cycling attacks, although the exact mechanism is not specified in the email.

To mitigate this risk, it is suggested to implement the interleaving approach for presigned transactions. By doing so, any new transaction would replace all previous transactions in the chain. This method aims to reduce the chances of mempool split and enhance overall safety.

In conclusion, the email proposes interleaving presigned transactions based on fees as a precautionary measure against mempool split and potential replacement cycling attacks. The author recommends implementing this approach to improve the security and reliability of the system.