Get a specific entry by its index or number?
I don't know whether you've seen the batch Twig filter? You may find if useful to accomplish exactly what you are trying to do, but with a little bit less hassle.

From the example in the link above:

{% set items = ['a', 'b', 'c', 'd', 'e', 'f', 'g'] %}

&lt;table&gt;
{% for row in items|batch(3, 'No item') %}
    &lt;tr&gt;
        {% for column in row %}
            &lt;td&gt;{{ column }}&lt;/td&gt;
        {% endfor %}
    &lt;/tr&gt;
{% endfor %}
&lt;/table&gt;


And here's what it outputs:

&lt;table&gt;
    &lt;tr&gt;
        &lt;td&gt;a&lt;/td&gt;
        &lt;td&gt;b&lt;/td&gt;
        &lt;td&gt;c&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
        &lt;td&gt;d&lt;/td&gt;
        &lt;td&gt;e&lt;/td&gt;
        &lt;td&gt;f&lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr&gt;
        &lt;td&gt;g&lt;/td&gt;
        &lt;td&gt;No item&lt;/td&gt;
        &lt;td&gt;No item&lt;/td&gt;
    &lt;/tr&gt;
&lt;/table&gt;


Essentially you're grouping your values into rows of a specific number (in this example it's 5). Then you can specify what to put in any empty spaces. So here it's the words 'No Item', but in your case it could be the middle partner entry.