References - TO:AR 6th printing, TO:AUE 6th printing.
Rules for Glancing Blow and Direct Blow are found on pages 78-79, TO:AR.
Rules for Arrow IV Homing Missiles are found on page 166, TO:AUE.
The question here is: do the Glancing and Direct Blow rules apply to Homing AIV attacks based on the Margin of Success on the roll of 4+ needed for it to strike a TAG-designated target? If not, do they apply at all, perhaps based on the MoS for the relevant TAG hit? I could see this being ruled either way, and it was not clear from the rules as written.