Getting rid of the Coordinator in the IOTA Tangle is a challenging task, especially regarding the network trustworthiness. Using a customized testbed, we experimentally analyse the functioning of the GoShimmer, IOTA's current implementation of the decentralised Tangle, with respect to specific network performance metrics. We observe that a trade-off exists among such metrics. We thus propose to determine the optimal rate allocation through an optimization problem maximising network performance and user utility. We further propose a distributed and asynchronous scheme to allow nodes to solve such problem.