Hi Jim,
I think Derek has the right idea. Having lived and worked in a number of places with uneven step depths, then always trip you up and cause falls (fortunately m current house only has one step that is shorter than the others, only fallen once because of it). You are doing a really superb job on this model, I have enjoyed watching it being built.
Regards,
Gerald.
PS I am going to make some Mint chocolate chip cookies soon, so if any of your Elves start swimming north on Lake Ontario you will know the cause.