Did you check the chassis with a surface gauge off of the table to be sure it's moved ?
If it has moved the correction can be very time consumming . Without taking away the integrity of the metal I would sugest placing a metal block the same thickness under the high points and palying heat there . Wait to see if the pulled area moves back to position . This can be a cat and mouse game . I've been successful straightening metal bars with this method within a few thousanths of an inch.
Is the 1/8th in a place it will be a critical factor ? Yes , I know you'll know it's there .
Gonzo