This is interesting! I heard a lot of complaints about the Xero API, it has low rate-limits and you need some workarounds to push data in at a fast enough pace. Definitely not the system to be used at scale.

One thing that is in the roadmap is to bring data from Xero so that you can interact with it in Decimals. It should give you a much better API, and we make sure it's going to get synced in the background. Let me know if this is something you might be interested in getting early access.