If it were me, I'd do it just as you're describing. Either way, I'd definitely put the Sora on the Felt.

Really the only thing that might give pause about the Ultegra going on the Torpado is that you might find yourself deciding against riding it in certain areas because the group could draw a bit more attention from potential thieves. This may not be an issue for you depending on where you ride and whether you always keep your bike in view. I can say that I'm more comfortable leaving a 105 bike locked up visibly at work. An Ultegra bike I would typically want to lock in an opaque bike locker.