Custom Activity Node - Encoding

I have a need to do an external call (Web Service) and return a potentially complex HTML string for use in a email. I would like to be able to encoding the string on the webservice side and decode it on the flow side before applying it to the email. It seems like the Custom Activity node does but every test I've run returns the same string out as goes in.

My settings are:

Activity: Encoding
Action: convertStringToCharEncodingBytes

charEncoding:
input:

charEncodnign:
input: 
output: 

But the output string comes out the exact same way as the input string. Am I missing something obvious?