The residential tables list the allowed wire sizes for a 100A-400A service. There is no mention of parellel s.e. conductors. Questions:
1. Is a 400A service the max for using these tables
2. can you run parrellel conductors sized to this table for services over 400A or do you have to go back to 310-16
3. If one 4/0 al is good for 200A would two 4/0 al be good for 400A
note: the allowed 400a conductor is 600mcm al which has a significanly larger area than two 4/0!!

1. You are correct in that the table 310.15(b)(6) permits service conductors, or feeder conductors that are the main power feeder to a dwelling unit
to have a rating of 100 amperes to 400 amperes. The conductors in this table correspond to the ampacity rating of the service, feeder or overcurrent device. This table does not indicate that the conductors in this table now have a new ampacity than the table 310.16, but only that they may be used in conjunction with a specific size service, feeder, overcurrent device.
2. Use of the conductor sizes in table 310.15(b)(6) is for a single set of service or feeder conductors not to parallel sets of conductors . If parallel sets of conductors are to be used than the ampacity table 310.16 must be used.