most people choose not to feed on the substrate because of the risks involved if the snake was to take in bits of mulch, wood, or w/e you have it on. my personal reasons for not feeding in the viv are mainly that one, but i also would like to avoid training the snake to think that everytime it's container is open, food is being tossed in. i dont know if it works, but i've never been bit since i started feeding in different containers.
so far as handling, it'd be like eating the largest meal you possibly can, and then trying to go run a mile or two. same concept, it's just to avoid regurges.