VFF's used to be a bit of a fad in the ultra community. We do see people show up with them at the start line. Unfortunately, we rarely see them at the finish line because they drop early.
I would suggest that if you find VFF's painful for long distances then you consider slowing down your training and building endurance adaptations in your feet before trying again. After all, it's those adaptations that you wanted in the first place. By slowing down your training I mean running to the distance you can before your feet hurt but do that distance more often that week.
Frankly, if you're not prepared to do the training required then a more comfortable VFF for long distance is called a shoe. Spend more time training on distances that don't hurt or give up and go for a shoe.