I took the coastal route from Wakayama to Yokohama, went by Hamamatsu on the Atsumi Hanto. Would be happy to provide any insight in which you may have interest. There are some pics in my member gallery (pages 8 ~10 with other trip pics mixed in).
Thank you for the advice about Rt. 1. I've never liked riding it around Tokyo and Yokohama, but there are worse roads. I want to get to Hamamatsu in one day, so thought the most direct route might be the simplest. The map references are excellent. Maybe I will ride with my wife (who had planned to take the train), but skip the first part and take the train past Hakone to a convenient place to start the coast route.