I would suggest you purchase this control neg.

basically the machine needs to be set up for normal, under and over negative densities.
this negative when properly balanced in help *analyze for the different negative conditions and compensate colour and density for your print exposures.

The printer I use *Lambda * has a 21 step dye program along with the *Shirley* lady for reference. But when balancing the different papers ect. we only read the step wedge and balance for nuetral grey and equal density steps between white to grey.

Using a grey patch negative after your machine is totally acceptable to see if you are basically in balance day to day, but I stronly recommend you use this control negative you mentioned to balance your machine.

One is necessary. to control the different slopes you will encounter with foreign film.
The other is a quick saftey check for day to day operation.
I hope this helps