Create in house profiles... printing from machine to machine is different... humidity... temperature... are all variables... you can half *** it like most people and adjust the levels yourself, or you can do it the correct way and start creating your own in house profiles...
After yo dial your profiles in, Try printing this test grid file......I created it with a program called Catzper. It should help you find the correct color to get cool gray 5 on your machine. Print it, then compare the output to what you want to hit, id the proper square then sample that squares color in photoshop and use that color value in your design you need to print.
I did print out out but it was a screen, not solid, 29% black (the CMYK equiv.) The other colors I printed using hte density control only check box and they came out a nice solid. This "gray" didn't seem to act the same way.
Cool Gray 5 should be set to the spot color in Illustrator or 15% C, 9% M, 8% Y, 22% K. Period. If the output does not match cool gray 5 you need to recreate your profile or create a custom color in versaworks using a pantone swatchbook. You shouldn't be adjusting color levels in illustrator to achieve a color, because the problem is not your file -- it is your profile.