Let's work with the 8' wave every 8s a little. The calculation gives a wavelength of 125'; so that makes the wave crest to bottom of trough distance ~60 feet. From the bottom of the trough to the middle of the next wave face is about 30 feet; so if you are in a 30' boat your bow will be digging into the middle of the next wave when the stern is at the bottom of the trough. You also have to consider the fact that you are moving forward into these waves (not sitting still) and the time that you will be going from crest top to crest top will be much faster than every 8 seconds. The sailing would probably be rough and uncomfortable, possibly dangerous depending on wind conditions. I'm not saying that every combination of H=T will produce a dangerous situation; but the "rule-of-thumb" that I read was if T is equal or less than H it can be bad.
I can't comment on your sail up the coast; we have not had the need or desire to go on a long passage yet. The California coast can be treacherous; I'm sure you are aware of that. With winds regularly 35 kts in the slot and steep chop in the gate we get enough white water to keep me content with weekend trips.
Plan your trip around weather windows and you should be fine tsingtao; take your time traveling up if the weather is not permitting; people tend to get into trouble when they are rushing to get to their destination. Some say that the winds are lighter and more consistent farter offshore; but then you are farther from a safe harbor if it gets bad or the fog comes in.