Hello friend!
I agree with you, it is not safe to shop at sites that are not known.
It is also true that certain aftermarket parts do not fit, I have the original rear diffuser mitubishi installed. Mine was one of the first to be installed (maybe it was the first).
What I see more interesting in this kit is the front. There are few options for the nose of the European sportback.
Besides the very expensive original Ralliart lip, can only be replicas of the lip, in China, Malaysia or Singapore (and one more in carbon fiber in the U.S.).
Another option are the lip of scorpion motorsport offered on ebay, and a few others. But the shipping prices are very high.
I have recently done an experiment, I have adapted the rear sedan espoilers in my sportback, and the result is very good if you have installed the diffuser.
Greetings...