What did you use to protect your cables??
15mm black irrigation pipe, got plenty of those here.
And overload protection?
An idea that has been discussed:
Get the right ones though:
Fuses as per panel spec?
So no circuit breakers or surge arrestors??
Sure, you can put surge arrestors in the combiner box. That’s usually where I see them. You can put breakers in there as well, if you really want to, but fuses are more commonly used. Cheaper.
Remember also, the panel can only do its I_sc current when you short circuit it, and your fuse/breaker and cable has to be higher than that (by about 20%) anyway. Unless something catastrophic goes wrong, the fuse/breaker is never going to blow. By using breakers, you are implementing an easy-reset which will never be used, and cost you extra money 
MCB’s can also be used for on-load isolation of the circuits. Pulling fuses on-load is do-able but can be a bit scary to some people.
I don’t like fuses in this scenario because as you rightly state they have to be just a little bit oversized to have any practical worth. That means you are at the mercy of a nuisance fuse blowing. Now you would be faced with the prospect of spending time fault-finding and waiting until nighttime to replace the fuse.
Of course, you could have faith in your testing and replace the fuse on a possible fault, not just on load.
Which is a whole order scarier.
I like the circuit breaker concept especially if you have combined 2 arrays. See: Undoing overpanelling by adding an MPPT - #13 by Richard_Mackay
I would want to see the current each array is drawing at any stage. This is easily done if you have a CB rather than disconnect fuses or switches…