I'm afraid there isn't much benefit flying DL as SM. Aside from one additional free baggage allowance, F upgrades chances are near 0, except for west-coast routes. Your chances is slight better for C+ but that's also not a guarantee. I often use my FO (old name for Silver, Flying Orchid) for early exit row seating.

I did get one SEA-JFK upgrade last year but that's after flight was significant delayed, and everyone booked away from the flight. Only then, might you have a shot at F.

Personally, I wouldn't waste your effort on a SM match, as the benefit gain is too little. DL AMEX will provide you with one additional free baggage and priority boarding. You can only get a lifetime match to DL program once, why would you want to waste it for a SM status?

Jiburi