I like this way but takes longer.
I do it all the time.
Here are the bits for fiberglass. They are carbide and coated.
I start at the edge sander
Drill press chuck is up all the way, I crank the table up for depth of cut.
Your riser needs to be full width and flat so you can slide it around on the table
after doing it this way I noticed the shank on the bit rubs the shelf above the cutting teeth so I made a pattern/rub collar to get a nice finish and shape. I don't have a picture of it.
Rub collar has this curve for the shelf