I have done this route 3 previous time with the Ebisu. The Kogswell, by the nature of the slightly higher frame weight and noticeably heavier components, felt weightier on the ride. The standard-size tubings still provided me with a fairly springy and responsive ride. The Soma B-line 37mm tires are no Hetres, but plenty supple enough for the horrible pavement in Pt Reyes National Park. Though there is a some weight up front in the small front bag, it wasn't nearly as heavy as the porteur set up, this in combination with the larger saddlebag leads to a handling that was more lively--though on most occasions it was very predictable and stable, on climbs I find the front end wander more than I am used to.
The fit on the Kogswell is very good for me; I was comfortable, and was able to stay on the drops for extended spells, which was especially useful on the stretch of super headwind toward Marshall. The P/R did an adequate-to-good job, but it will return to Porteur duty today. I will probably ride the Ebisu for the upcoming brevet, or maybe take the soon-to-be-repainted Sequoia.