I ususally use the bake strips for my larger cakes. I think they make the batter bake higher and straighter up the sides and with less of a curve at the top edge. I also use the flower nails, although not both at the same time. The nail conducts heat up thru the center of large cakes to make them bake more evenly. Without it I have to bake my bigger cakes quite a bit longer to get them done in the center. I use my large nail for the larger cakes. Works great, love it.

As far as using a nail in place of the heating core for the stand up bear I wouldn't. You need the depth of the core for that deep cake. And if you put some batter in the core it'll bake a nice little plug for the hole the core makes.
Pretty neat and simple.

I do use the upside down flower nail in my big sheet cakes and as I said I do use 2 of them. I have a very old flower nail that is pretty big and then I just use what I got at Wal-Mart. Ever since I started using the bake even strips and my husband made my oven level I never have to cut off a cake now. Its great!!!

Over lunch, I went and bought two flower nails! gonna try this with my cakes tonight!!