I came up with a workaround. It assumes that the trading class string will show up in the char* Asset string (the IB Asset code). I will document it here.

Basically, I encode a 32-bit unsigned int into a readable char string. This string gets copied into the CONTRACT struct.

"__abcde\0"

So my plan is to parse the IB code for the first instance of the double underscore "__".

Then the five characters ("abcde") can have up to 86 values each, giving me 86^5 possible values, which is greater than 2^32. I have some rules:
* The characters must be readable by a human.
* The characters must be able to be typed by an ordinary keyboard.
* The characters must be nonzero (not a null character).

Finally, there is a null character to terminate the string.

I will be testing this soon.

How about using the Zorro code also for your plugin? It is relatively easily to generate from the strike, expiration, etc. The class is stored at the begin of the CONTRACT struct and the exchange is converted to a number and stored in the Type field. That's all data you need. I can give you some code for the conversion.