I just tried a dummy booking online and yes, it will accept that routing, although the only real Delta metal from SEA to SFO is via SLC.

There is always a possibility that they allow another carrier in the mix (NW or CO for sure and maybe Alaska). Anyway - I'd call and check. If only delta metal can be used (or is your preference) then I'd book online using the advanced booking feature under award booking that allows stopovers.

Remember, a stopover is a stopover only if it's on a valid routing between point a-b. Some valid routings might not be obvious to the observer. North America flights should be "tried" online.

Remember you can have a stopover or open jaw but not both. The width of the open jaw cannot exceed the length of either of the other two segments.

So for example, DFW to SFO, then JFK to DFW is NOT a valid open Jaw.

Some cities have "co-terminals" so flying into SFO and out of SJC is NOT an open jaw.

Stopovers are one of the best features of Delta's awards that United does not have (for domestic tickets). They increase the value of the ticket a lot IMHO.

Billy