GPU position in rigg? 1060/1070/1080ti


So I have built two mining riggs. And I’m wondering how I should place the GPU’s. Currently I’m running with 9 cards of each rigg, but a bit confused as to what to put where.

My riggs are setup like the following, I have 3 rows.

Bottom Row (A): room for 6 GPU’s.
Middle Row (B): This is where the PSU + motherboard etc are, naturally a lot of the heat from Layer A is stopped by layer B, giving Bottom Row (A) the “worst” ventilation
Top Row (C): Got pretty good ventilation significantly lower temps here

So now I have the following setup, most GPU on top row due to temps.
----------------------------- 6GPU
----------------------------- motherboard + psu
----------------------------- 3 GPU

Now my question is, what cards to put at bottom row? I have several 1080ti’s from different brands, and espcially the Evga cards are keeping temps pretty low. On the other side I got the zotac cards and asus rog strix cards that run a lot hotter.

I got 4 1070ti’s and a 5x 1060 6gb (not using all, gonna ebay some of them).

So what do you recommend? Currently I thinking about keeping the 1070ti’s and the lowest temp evag 1080ti on bottom row?

the idea is that the highest temp cards are on top. But could be wrong since the different cooling solutions could affect it, it seems to me the 1080ti sre moving a lot more air than the 1060, but 1060 a lot higher temp