Standmount speaker... Cardas Method or manual

Big difference even from starting point using Cardas Method and speaker manual
Each room is different, as are the speakers. The Cardas method is a good point to start from, but it is not always the best for many rooms. A good way to find the correct position for placement is to start with a equilateral triangle from the listening position, then the distance from the wall behind them, adjusting for bass output. Then, adjust the width the speakers need to be from each other. Lastly, work on the toe-in of each. It may take several listening sessions to get them right, so don't get in a hurry. Have fun!
The room dictates where the speakers will sound best. If you have had speakers in this room before your starting point will be the same place where you used your previous speakers.
There is not one method that is best for all rooms and speakers. For example my Spendor S 100s sound best angled in so they cross ahead of the listener; this is the factory recommended setting. My Gamut L5s sound better pointed straight ahead; again as the maker recommends. It is very unlikely that the same spot will be good for both. Cardas is a good starting point; try that and then try the position in the manual [or vice versa] and see which you like better. But that is only the beginning; to get the most out of your speakers you will still have to experiment. The only manual you can absolutely trust on positions is the KAMA SUTRA! LOL.