I didn't say 4x4gb is a bad idea, i said it is the least recommended. Mixing 2x4gb with a single 8gb stick is really a bad idea.
Why is the least recommended in your case: They are not bought as a kit 4x4gb so no one can guarantee they will work without problems. Each kit is or may be cut from different silicon and may have minor differences in primary, secondary or other timings which can return errors. Odds will be in your side if they are exaclty the same in frequency, timings, capacity, voltage, rank etc.
Also populating all ram slots will put a higher load to the memory controller of the cpu. that's why i recommend selling and buying 2x8gb of ram.