MacBook Pro has 'wrong' RAM - should I replace?

I am the 2nd owner of a late 2011 17" MacBook Pro. I am using it for video editing.

The first owner doubled the memory from 4GB to 8GB. Unfortunately at the same time he reduced the speed by replacing 1333Mhz modules with 1067Mhz modules. The Book has passed an extended hardware test (by Apple) so I know the installed RAM is OK. But I note the that the minimum spec for this model is 1333Mhz. So would I benefit from replacing the 1067 with 1333?

Also, Apple says the RAM can be up to 8GB 1333Mhz but I have read that it will accept 16GB and/or 1600Mhz. Has this been verified?

Thanks.

Personally, at about $46 I'd replace what you have with a new pair of 4gb modules - 8gb of 1333 RAM