Neotope speaks the truth...There's no overweight charge for First and Envoy passengers for 2 bags up to 70 lbs.

From the US Website:
Overweight checked bags
+ $90 each
For bags that weigh 51-70 lbs/23-32 kg in Coach
(no overweight charge if you’re booked in First Class for first 2 bags)

+ $175 each
For bags that weigh 71-100 lbs/33-45 kg

Oversize checked bags
+ $175 each
Dimensions between 62 – 80 in/157 – 203 cm
There is a $125 fee per bag for checked bags 3-9.

And from the DM Preferred page for CP:
- You and everyone in your reservation are exempt from the first, second and third bag fees (group reservations not included)
- Your bags will be loaded last which means they'll be among the first on the conveyer belt at your destination
- Allowances vary by airline, so please contact the airline you'll be traveling on for details.