Hi Lucas,
In response to your question regarding speech mannerisms, Rule 10.1.2 tells us that the alphabetic word sign CAN be used with d, ll, re, s, t, and ve providing the resulting word is standing alone. In your example of “you’d’ve,” the “you’d” is not standing alone. In this instance, use the “ou” contraction in y(ou)’d’ve because once the ‘ve is added, the word “you’d” is no longer standing alone.
Hope this helps and makes sense.
Jana