Hi Thomas
Got already the I/O extension.
Pff 25 years , that mean you are Daddy's on CNC,
have you some on You Tube or links on your retrofitings ?
Any way I feel pleasure when I do this retrofit (even I headache on manuals) and like to understand each step and all about my machine.
attach explanation
Done some work to my main PC, ....a midplatte for wata' cooling, but it seems glued the sandwich is not the best, I must redo on CNC and use some gasket between plattes.