Hi TRS
let me take a stab at this;
300-4(d) states "installed and supported so that the nearest outside surface of the cable or raceway is not less than 1 1/4" from the nearest edge of the framing member."
so i guess as long as you use the outside entries into your deeper boxes, you are NEC compliant.
temperature rating as applied to those cieling mounted halogens seems to be something i have not grasped as yet.
i have a customer who has had me install two so far, cooked the 90deg new NM both times.
obviously i am overlooking something
perhaps others will comment..