OK, I have a preliminary test version of a motor controller. Two MOSFETs in parallel (on the perfboard).
First time through it was OK with 12V, when I switched over to 24V it biffed right way [Poof!] Drain to Gate short x 2. But, I didn't use a clamping (commutation) diode. When I re-built it I did use one and it's performing well.
So, as far as I am concerned, that MOSFET zener-equivalent diode is not suitable as a clamping diode.
Next step - mount it on the deck with the chain on, get some load on it.
- And, yes,.. I'll have to buy some better spec'd FETs or parallel more of these (2, 3?).