I’m sorry but your question supports my argument. You indeed can’t make the changes Xibo needs to support large file uploads, therefore the hosting you’re using isn’t suitable for it.
Yes I’m making a generalisation about shared hosting, but in our experience we hear from lots of people who have their shared hosting accounts disabled for using too much CPU time/too many MySQL queries etc when hosting Xibo on low end shared hosting accounts. If your provider is the exception then that’s great. Hopefully they’ll also allow you to make the changes Xibo needs to support large file uploads.
I’ve logged it as a Feature request here:
Hopefully someone will feel like taking that on as a project.