I don't think the Small Sugar will be contained on a 3x5 trellis, but I guess you could always let it trail over the other side. Experimentation is always fun. You could trail one plant and prune another - see which works best.

I am planting New England Pie (which, I believe is basically the same as the Small Sugar) because it is supposed to be the best for pies. I will be trellising it up, but I have some old wood pallets (that I deconstructed) that are 8 feet long. I am hoping to sink the verticals 2-2.5 feet into the ground for stability, and then add some extra height to make a trellis that is 7 feet tall and 4 feet wide. That would be tall enough to let it roam free, and I figure I could prune the ends when they reach the top, so that the plant can put more energy into the fruit. By that time I figure each plant will have 3 or 4 fruit. Most pumpkin growers recommend pruning the vines once the fruit is set anyway.

Personnally, I wouldn't try to vine something that may be a "bush"-type variety. It probably wouldn't work that well.