A 37g with 28 neons and a handful of guppies sounds pretty neat. Both species have very different personalities, so it would be interesting to see them interact. Make sure to keep 1:3 male:female ratio for the guppies, otherwise, the males can get nippy. And neons would be helpless to a bully. (Although, I can't imagine a bully guppy being anything more than an annoyance. He wouldn't hurt them.) Also, guppies, like platies, are pigs at feeding time. They'll hog all the food at the surface of the water, so you might try to find a food that is made for mid-water feeders also.