Like others have mentioned it's not possible to have more than 1 Cache disk per disk group. I have the same advice as the others, pleas do more than 1 diskgroup.

So in all that would mean for you (per ESXi host):

DiskGroup 1:

1 x 1.46 TB Cache

2 x 3.49 TB Data

DiskGroup 2:

1 x 1.46 TB Cache

2 x 3.49 TB Data

This way you would potentially only need 1 Cachen drive extra per host.