Doable on S05 Pro 4x4 or is a 1" surfacing bit needed? I recall reading something about it not being to reach the back end of the MDF slats but may be mistaken.
If yes, what should the feed rate and stepover be? Not worried about time efficiency.
The #201 is tiny compared to a fly bit. C3D sells a carbide insert one. There are others. I have a Whiteside 1" 3 cutter one. The key for a fly bit is shallow depth of cut and fast IPM. The 1" or larger bits have a lot of engagement and tend to burn if you try to take off too much or go too slow.
I dont have an SO5 but here is my Whiteside 6210 custom tool.
I have surfaced my waste board (Shapeoko 4 pro) with the 201 using default F&S with no issues! I think in theory it would be best (ignoring time) to surface with the smallest bit possible, but the implications are probably negligible. I also recommend using a V bit to carve a 1" grid on the waste board.