Hi all. I'm looking for ways to improve the way we create a particular assembly; in this example it is our insulated floor.
 

All projects will use a similar floor, the difference being either the length, width or wall panel thickness (any one of these could be different from the previous job). There are always two internal components; the "concrete plinth" and the "mock enclosure". 

These two will always stay internal as they're never drawn as individual components and are reference only.

I would like to drive the length, width & panel thickness parameters by equations in the assembly:

This all works well and I'd like to use this as a template assembly. However, my problem comes when I want to save this template for a new project and change the variables accordingly.

I always get the "Equation x not evaluated because dimension is read-only" warning:

I've tried pack&go, save as with references and copying, pasting and renaming in a new folder but it's always the same.
 

How can I stop this occurring and begin to use this as a template assembly for future jobs?

SW 2025 SP4.1

TIA!