Rick, I did cut the tap root on both large adeniums when they were 6 weeks old. I'm pretty sure I cut the tap root of the 3 small ones as well. The small ones were from a batch of seeds that I had ordered from a Thailand vendor through Ebay. They were not fast growers so I decided to keep them small by placing in gritty mix in ceramic bowls.
The seeds of the larger adeniums came from a US vendor through Ebay, and they were my very first adenium seeds. And when they grew these large caudexes and succulent roots I thought all adeniums grew this large. Then come to find out in discussions on another thread that most seedlings do not have large caudexes.
I recently contacted the US vendor telling that I wanted to order the same kinds of adenium seeds. She informed me that she doesn't sell adeniums anymore.
I had sold most of my large adeniums, but I will keep the remaining few and isolate them from the Thailand trees in hopes of propogating seeds from them for root stock.