I can't answer your question but think the combiner in you situation may make sense, as when you have three or more strings (4 panels paralel) you really want to fuse/breaker them so that two or three of the other panels don't damage one if something goes wrong. Ie: three panels feeding into one would be much more then the ones rating.
Don't get me wrong I have run them that way with out fusing but it was on things I didn't care about.
Even on my big aray I just cut the mc4 wires and spliced, I have heard this may violate your warrenty but I also believe more people do it that way then not.
I hope this helps
gww