I have to say I'm not the biggest fan of Gilliam playing RT in these preseason games. Even if it were true that he's more comfortable on the right side, there's a very high probability that we'll need Gilliam to play on the left side at some point this season. He needs to be getting those reps on the left side right now in preseason while those learning reps are still harmless. Gilliam already has plenty of reps on the right. At the very least, they should have Gilliam splitting 50/50 during the preseason.
Conversely, Sowell already has experience at LT and isn't benefiting nearly as much from the additional reps there.
Maybe Gilliam is one of those guys that is more comfortable on one side. Fair enough if true. That said, Gilliam was pretty bad at RT last year until the up tempo scheme helped cover up the stink in the 2nd half of the season.
Not only that, but Ifedi's long term future is almost certainly at RT. Gilliam's most likely path to starting long term is at LT.
I get that chemistry and continuity matter on the OL and that Seattle wants to set their starting line as quickly as possible. But I also think that Gilliam's lack of experience at LT could seriously bite us in the ass this season if forced into action at some point, which IMO is likely. Now's the time to get him some reps and experience there.