On data websites, they say he is like 5 foot 3 or 5 foot 5, how is this possible if ryoko and the girls are at least 5 foot 8 and he is usually seen as tall or even taller than them?

According to this image, taken from one of the official art books, Tenchi is a little less than 156cm. I'm not sure what that is in inches, but as you can see, Ryoko, Aeka and Mihoshi are taller than him.

156cm = 61.42" or about 5'-1½" This is somewhat short for a man, even by Japanese standards. However, I believe at the very beginning Tenchi was supposed to be 13 years old which means he wasn't quite full grown. By 16 years old he should have reached his adult height.

On the main site here some character heights are listed as:

Tenchi: 5'-3"
Ryoko: 5'-6"
Aeka: 5'-6"
Mihoshi: 5'-6"
Kiyone: 5'-8"

But I've seen Mihoshi listed as 5'-10" before so I don't know if there is a definitive answer to how tall any of the characters are.

In this image, three of them are nearly equal height: http://www.henheart.com/images/tenchigroup4.jpg

And here four of them are very close although Aeka may be slightly shorter: http://www.henheart.com/images/tenchigroup9.jpg

Here three of them at left are equal height, but Ryoko and Aeka are in heels which implies that Tenchi is taller. http://www.henheart.com/images/tenchigroup8.jpg

^_^;;

Actually Tenchi was about 15/16 in the first episode. Being about 5 feet tall sounds ok for a Japanese teen in '95.

Hopefully he they can state he had a growth spurt by ova 3, cause he seems to be as tall or even taller than most of the women. I reckon by the time GXP starts, seina is the height tenchi use to be, while you can see how tenchi is now in comparison when they stand together.

Look at this, now tenchi looks only a little shorter than mishoshi.....if she is 5 foot 10, he has to be 5 ft 7 at the least
I think its just her hair that makes her look taller

Yeah I've always got conflicting data about how tall characters are, how much they weight, etc. I generally put the stats on the main page according to the webistes that were available at the time some were different, but I tried to get a general consensus.

I'd go by the official books rather than sites.

When did he contradict Tenchi's height?

When we see him taller than ayeka or as tall as ryoko in the ova, or this is just the case of lazy animators

I don't recall any scenes like that.

Maybe not so much in amine, but in manga I often see a character's physical height or build modified based on context. They'll make a guy larger and more imposing when he happens to be in charge of the situation. When the spotlight switches to someone else, then they will be drawn smaller or more normal sized. In the case of Tenchi, it could be lazy animators, but more likely it is artistic license being taken.