How can I transfer an upgraded / custom design to another installation without affecting anything else on their setup?
In v8 if you have 'Designer' you can choose to deploy a partial site snapshot that will include only the files that a customer would need to import into their site to get it looking like yours.
You can do this by going into Design | Deploy Partial Site Design. This option allows you to enter a description for the design you are exporting. You can then choose the Layouts, Selectors, Variables, Conditions, Content Category, Property Tab's and any other specific files to be exported in the design to enable it to function as designed.
In v8 if you have 'Designer' you can choose to deploy a partial site snapshot that will include only the files that a customer would need to import into their site to get it looking like yours.
You can do this by going into Design | Deploy Partial Site Design. This option allows you to enter a description for the design you are exporting. You can then choose the Layouts, Selectors, Variables, Conditions, Content Category, Property Tab's and any other specific files to be exported in the design to enable it to function as designed.