Yes it will stretch the screen. But 100% of the people who see it can't tell that it's stretched. Even side by side with a 3.5" it is almost impossible to tell. Small screens hide a lot.
You can tell pretty easily, it just doesn't bug most people.
Also, some 4.3" support 4 and 16:9 switching.
One more thing. Dalian? Really? Unless you're making the world's smallest or best portable, it's not worth it. Over 100 dollars for a screen is insane in my opinion.