We have been doubling the thickness of half soles on tap shoes for a while. The folks who use them (sadly, none of us at the shop!) say it increases the volume of their tapping. The shoe pictured had a couple things done to it.
1. The "half sole" , or forefoot section, had the thickness doubled in leather and the tap installed.
2. A grippy rubber piece was added for traction and balance behind the tap
3. The heel height was also increased in keeping with the half sole increase and the tap was reinstalled.
The second picture is the cosmetically cleaned up final product. The coloring disguises the new additions and makes the edges shine like new.