Forum Discussion
And if you don't have a 11.5.3 partition, you should have UCS backup from before you performed upgrade. So you can install 11.5.3 version, restore configuration from UCS and then upgrade to 13.1.1.
There is a command cpcfg which you can use to copy configuration from one boot location to another, but one of the restrictions is that version of the target boot location must be the same or later than the version of the source boot location. So it cannot be used for downgrading.
If you don't have UCS file, you have to manually rebuild the configuration. One option came to my mind rigth now. But I have never tried it myself. If you have a cluster with two nodes, you can break it into two standalone boxes, downgrade one and cluster it again and try to synchronize the configuration and then upgrade the second box.