Homemade Mini-Spring Pack Leveling Kit

Hey guys. Had this idea after hearing so many people bad-mouth the use of the mini-spring packs on ebay. But there's not much to these, and if some of them aren't even made of spring steel (if someone could explain the difference to me, I'd really appreciate it), what's stopping me from throwing some plates together drilling a hole through them, and slapping them under my spring? So I'm looking for reasons and answers to the following questions.

Is there any support added to the existing leafs by going with some official DR pack as opposed to an ebay spring pack? Do the ebay types (plate steel from what I've heard) have any arch to them at all? If not, and I could fab some up on my own, what thickness steel do they utilize? Thanks in advance. And to please all the professionals out there, the $100 saved from building them myself would be put towards an adjustable track bar. Looking forward to the info in the professionally done VS. home made spring pack debate that is to come.