"For this reason, it is common practice in some industries to switch inductive DC loads with 2 sets of contacts in series, to distribute the arc effect. "
but I'd expect that to be the same fallacious logic that called for 4 engines instead of 2 on aircraft (proven to be wrong, double the number of engines and you quadruple the number of engine
failures per aircraft) and dual belts on alternators. Proven inferior to ribbed belts for the same reason that I'd expect dual relay arms to fail. One always winds up taking the brunt of the load, one relay arm will always close a fraction sooner, and then weld shut or wear out and cause the whole system to fail, sooner than one properly sized one would.
Relays: diodes, caps, snubbbers, all well and good and better than "just" a relay, but I had wanted to work with 'just' the basics, i.e. first start with sizing the relay properly. (And yes, eventually I found one that should be adequate enough.)
Again, thanks to everyone.