Question on Blends & Contractions

I am not sure which blend to use in some words.  For example "Clinton" (the city) could be written C-L-I-NT-N or C-L-I-N-TN.  My book shows the second but I'd like to know why.  Also "abandon" is written A-B-A-N-DN but my instinct is to write it as A-B-A-ND-N.  The simplified text gives no reasoning as to why they choose one blend over another.
Also I'd like to know the correct way to write "it'd" and "that'd".  For "it'd" I can think of two ways: IT+TED or I+TED with an apostrphe.  For "That'd" I think of THAT+TED or THAT+D with an apostrphe. The simplified text gives no mention of these contractions at all. 
Thanks for your help!

(by teacup25 for group greggshorthand)