I don't think you will have much success to get a transaction propagated which has less than 1.0sat/vB as transaction fee rate to offer. Sure, I can set my node to accept transaction that pay even 0sat/vB to include in my mempool, but unless you're one of my peers, it's not likely such transactions will trickle in and equally unlikely that my node can relay them to other nodes which usually have the default relay minimum of 1.0sat/vB.

Good luck with convincing any miner to mine transactions below 1.0sat/vB, unless they're their own transactions.