If you are trying to simulate a PRESS, then look into PROOFING with your Epson and and not so much G7. You can Gray Balance (neutralize the CMY channels of this Epson) and the results are good for regular printing of Images and Artwork.
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But you don't need to a G7 Calibration to do proofing. You just need a good Proofing Rip to drive the printer and perform the Match, hopefully, itteratively.