Gbro, The "spit" is for use when cookin' hogs over fire and/or coals... It will burn the bottom and leave the top raw otherwise...
I am guessing that bswiv used only the "hot box" on the end to hold the burning wood and the heat is evenly distributed by the time it reaches the hog...
I have never had a spit setup and really just grill my pork with a little smoke wood added for flavor only. I will wrap my large cuts or whole small pigs in foil for the first couple hours... then remove foil to impart the dark color and smoky flavor. I also stab slots into the pork to add fat back and fruits/onions etc to keep this VERY LEAN meat moist.
But, again, I think bswiv's hog is truly smoked, not bar-b-qued or grilled...
Also, true bar-b-que is far different than grillin' and I am no bar-b-que guy as it takes far more time and fuel.
Brent