[Coco] Design files for 512k or more CoCo3 upgrade

[Zippster]

Hi everyone,

Are there any design files available that anyone knows of for a
good CoCo 3 memory upgrade that are ready to go?  
Gerbers, Eagle or KiCad files or the like?

I’ve got a stock CoCo 3 that needs some more memory, and
I think I’d like to build one rather than buy one.

What’s out there?

From what I’ve picked up, it seems like the CoCo1 and 2 are
limited to 64k maximum.  Is this true, or has anyone ever made larger
memory upgrades?

Thanks,

- Ed