Would it be sufficient to save "level=5t" (5 volts TTL) or "3.3c" (3.3 volts CMOS) ? And also consider the issue that a "3.3c" but 5v tolerant (3.3v5t?) input can be connected to either "3.3c" or "5t" or "5c" outputs. I suppose we could tag pins with Voh, VihMin, VihMax, etc.