Welcome to the Board
I am not that familiar with the St. Croix offerings, but given your targets there are some other rods that I can highly recommend:
Meiser 11' 4" for 5/6
Meiser 11' 7" for 5/6
Meiser switch for 5/6
There are more expensive than the St. Croix, but if you can manage it they are well worth the added expense.
If you can get to a regional spey clave and cast the rods with a few line combinations, that would be ideal. Also, unless you are experienced as a spey caster, get some good instruction soon.
Practice is about increasing your repertoire of ways to recover from your mistakes. Joann C. Gutin