Hi @dickfickling thanks for posting! Do @ben 's comments on this post answer your question?
The max body size for requests in Retool hosted (cloud) instances is 40MB.
For on-premise installations, there isn't a max body size. This is limit is applied at the networking level (I believe the nginx default is 1 MB), so if you're using a load balancer or a proxy, I would check and see if the limit is being applied there.