Hello,
With a sanding Drum, thickness sanding must take measures to control kick-back. Here is an old thread about this topic:
https://forum.shopsmith.com/viewtopic.php?t=582
The Sand-Flee is not really a thickness sander, but it will make a surface flat, and it has no worries for kickback.
There is also a Sawdust Session on using the Conical sanding disk for thickness sanding. I have done that successfully but I need to work on dust control.