Looking on the internet deeply has found these results:

had major concern is the most popular phrase on the web.

had major concerned 18 results on the web	had major concern 1119 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Major Leopold concerned about this one? Mum's the word where the Major's concerned. In this context, FSO is in competition with existing production plants either belonging to the major manufacturer concerned or independent that could also produce these cars and would be interested in assembling them. The second major result concerned ourselves as consumers. Mum's the word where the Major's concerned. As we know, the Commission proposal seeks to open up major areas concerned with port safety to competition and does not guarantee workers' rights.	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

had major concerned

18 results on the web

had major concern

1119 results on the web

More popular!

Major Leopold concerned about this one?
Mum's the word where the Major's concerned.
In this context, FSO is in competition with existing production plants
either belonging to the major manufacturer concerned or independent
that could also produce these cars and would be interested in assembling them.
The second major result concerned ourselves as consumers.
Mum's the word where the Major's concerned.
As we know, the Commission proposal seeks to open up major areas concerned with port safety to competition and does not guarantee workers' rights.

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.