I don't know if it is long enough, but inserting a cake tester down thru all the layers while it is chilling might help. Another option would be to get a long cake dowel, sharpen one end, insert it down the center of all the layers, cut it off so it is flush with the top layer, then ice as normal. Doweling is used in cake decorating for stability.

Hope this helps.

Paula in TN

 

idea to keep cake from falling

Maybe if you just cut the upper layers a little thinner that would help keep it from falling. Put more fillling between the bottom layers and less between the top.