Around 6.5. "Viable" depends on what you want. A $300-400 book in this condition. My guess for selling, you wouldn't make extra $ for grading, but you wouldn't lose anything either. For collecting, that's a personal decision. Whatever your metric for investing for grading vs. the value of the book. For me, that starts with whether the book has some importance (which could be universal or personal). Then, if it's a mid- to upper-mid grade book like this, I'd like to see the cost of grading to top out around 20% of the FMV. Your thresholds may differ, there's not a wrong answer here (although I do see way too many people trying to sell lower grade CGC books for way more than they're worth, presumably to earn back their grading fees).