Well, I'm not going to "win" St. George, but thanks for the good wishes... I'm in the "just over three hours" group, which will get me in (or near) the top 100, if the running gods are willing. And yes, there is altitude to deal with there; the start is a bit over 5000'/1500m. There is amazing scenery to occupy one's mind along the way.
As for prime-searching, all of my long-running tasks have completed except for a PG SoB which will hang around for a few more days. So, I've grabbed a few Mega units and am crunching away on those.