Using Velocity Silver to upgrade to Delta Comfort plus
 

Yes, if they have seats it should clear without issue.

However the majority of routes will only have middle seats available. If you prefer a standard legroom, window or aisle seat (and you are seated in one), you may lose that seat in favor for a middle seat if you request the upgrade.

Personally, I don't bother anymore, because the seats are always gone.

Thanks CP,

I am keeping an eye on the flight, and it appears that all seats are wide open SYD-LAX on my outbound dates.

Just keep in mind, those seats will be distributed to all DL elites before you are eligible. By the time those are processed, it's unusual for there to be any scraps left.

While in the majority of cases this is indeed the way it works out, it seems the OP is flying SYD-LAX-ATL with SYD-LAX on the newly configured (28C/48F/90W/122Y) B777 which is an extremely high count of W seats compared to the rest of the fleet. I'd venture to guess (without providing specific load information :) ) that the OP has a very good chance of clearing into a good W seat if the seat map is indeed that empty. Keep in mind that while it's common for DL to oversell Y and issue an "OP-UP" (if you can call it that) to W, all upgrades from Y to W will be processed before resorting to this, just as it's done with GUC requests.

Now the domestic segment will prove to be more interesting. Not sure which LAX-ATL flight the OP is booked on, but if it's on the B777 departure at 8:15, it's the same configuration aircraft, just treated differently for the domestic leg. So in theory, OP can choose a Comfort+ seat (physical seat / service will be the same as Y) beforehand and apply for an upgrade to W again, which in this case would be to the Premium Select seats.

That's fair, I don't have experience on this new configuration. However this route does tend to be elite-heavy as it is the only Skyteam flight between the USA and Australia.

Thanks Widgets,

Domestic LAX-ATL sector is the 9.10am service. Sadly no widebody.

Then forget about C+ on LAX-ATL. It often fills up with Delta's top elites on that route, as LAX-ATL is one of the routes with the most Delta Medallion members frequently on board. The non wide bodies have so few C+ seats that they're often full weeks in advance on this route.

However, as someone who recently took SYD-LAX on the refurb 777 and say how many C+ seats there were, your chances for that segment are good.

I'll manage on that flight.

Definitely the longer flight is where I'd need the comfort.