In terms of tagging Dockery - I think he would get the O-Line amount. In
2006 the franchise tag for an O Lineman was 6.99 Mil. I think that the categories are set in the CBA and that, in 2006, there was not a separate category for guards. Unless the new CBA alters the categories, I think that franchising a tackle costs the same as franchising a guard. (For some reason, I thought they had separated out left tackles, but I could be wrong).
These numbers are from
Ask The Commish.com - The Cost of Applying the Franchise Tag in 2006 and were for 2006:
Quarterback $8.8 million
Defensive End $8,332,000
Linebacker $7,169,000
Offensive Line $6.99 million
Wide Receiver $6,172,000
Running Back $6,085,000
Cornerback $5.9 million
Defensive Tackle $5,656,000
Safety $4.1 million
Tight End $3,327,000
Kicker/Punter $2.5 million