For a "snubber" which is not design but diagnostic the whole approach changes.
The need for better understanding with such thing has become a real challenge.

 

Electronic fuel injection has been around for many years. One option might be to see what others have done. Even some high-reving two-stroke motorcycles have used it, I think. Looking at one of those circuits may be very educational.

Good point regarding fuel injection; that was also mentioned previously. I have seen a 33-36V Zener from MOSFET drain to ground used for fuel injection circuits.

I have been waiting for some capacitors and new MOSFETS to arrive because I destroyed all my SiS176LDN MOSFETs and the IRLH5030s I ordered from Newark are taking a while. Then I am going to experiment with drain-gate capacitors as @ronsimpson and @Danko have suggested.

The NID6002N discussed hereinbefore appears to be a discontinued product but I found this BV1LB085FJ-CE2:

Automotive 1ch Low Side Switch IC ■ Built-in overcurrent limiting circuit(OCP) ■ Built-in thermal shutdown circuit(TSD) ■ Built-in active clamp circuit ■ Direct control enabled from CMOS logic IC, etc.

It just arrived yesterday and I am going to test it shortly. Given the price of the MOSFETs and Zeners I was considering, it's not appreciable more expensive and seems to be very well suited to my application specs.

 

I'm going to post the results of my experiments here just in case this is useful to anyone in the future or otherwise:

BV1LB085FJ-CE2 (magenta gate; yellow drain):

The problem with this one was that the current didn't seem to be exceeding 1 amp (should be 4+ amps). There was no Vgs vs Id-s curve in the datasheet but the overcurrent protection curve mislead me into thinking it would work.



FQB34N20LTM 200 V MOSFET with a 62V Zener (SZ1SMB5944BT3G) and Schottky (PMEG060T080CLPEZ) combo accross the solenoid (magenta gate; yellow drain):

This was supposed to be the 'big guns' ultra-speed high voltage Zener scenario that knocked socks off ...but I did not feel like the discharge was appreciably faster and the gate showed some sort of transient spike at solenoid turnoff.

Furthermore, I somehow managed to destroy two FQB34N20LTMs in a matter of 40 minutes, even with the 200 V D-S and avalanche ratings. I have some superpower that shorts Drains to Sources. The second one I hadn't even powered on yet - so I think I might have shorted D-S just from soldering too hot/long. I ordered 5 more to reattempt this.