Customize UI screens in Ofbiz

Hi Ofbiz Users,

I'm working on customizing ofbiz as a ERP solution and the requirement
comes to having less number fields in most of the screens than what comes
out of the box, this requires changes in .ftl files and Forms xml, in the
past i have been commenting out the fields that are not required or use
access privilege to limit the fields that are being displayed; however this
requires merging all these changes when i will be upgrading to the new
version; please can you advise what is the best way to handle this, Any
pointers appreciated

Regards