Edzard,
thank you for the questions, to think about points. First of all most of the people on the Forum aren't perfectionist like you. Few of us can create a " Japanese garden" in the purest form. I know from my experience that I won't. What I like from the Japanese style is the simple lines, harmony with the plants and rocks mixed with my " feeling good about my garden". As I seen pictures posted on the forum, there are many gardens people are proud of and you won't approve it. It is OK.
Why I asked about the proportions? I've seen lots of different gates, many of them "just didn't look right". I would like to copy something from a book, but I'm not willing to spend ten thousands on a bamboo fence or put a gate inside my yard where it just would look stupid. I need the gate at the top of the garden, going out to the back lane. We never come in through that gate, just go out to do some pruning or watering the plants outside.
Why we admire the Japanese style? It evolved during hundreds of years, followed tradition and observation, religion and myth, practice, necessity and needs until it became perfect. You have to know all the rules because you are a professional garden designer. It is hard for you to see something what isn't perfect.
I never claimed to have a Japanese garden. I will have this fence because I like the style and the color. And I need a gate to go to the back alley with no more road from it, in a cul de sac, next to the ravine and trees, bears, coyotes...etc.
BTW I'm 165 cm tall and shrinking.
Andrea