Squid installation on extroot

Hi there!
I know that a solution was found for the question but I just wanna register that latest instructions on openwrt.org about extroot configuration gives something good to work with, also I wanna ask about Mount the new storage in /opt since it is not covered on it and, of course, actual flash does not have /opt. Would /overlay replace it?

Why should we have /opt mounted on external storage since that extroot configuration, depending on how it was done, already gives plenty of space to install packages and store squid cache, for instance. And this is where I wanted to get to.

Any ideas about setting squid up following this extroot configuration without /opt? I have already give it a try on 1. Squid transparent mode on devices with sufficient space to install Squid.

Would you say that squid should accept following setup in order to work gracefully?

root@LEDE:~# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/root                 2.3M      2.3M         0 100% /rom
tmpfs                    13.8M      1.9M     11.9M  14% /tmp
/dev/sda1                10.9G     60.7M     10.3G   1% /overlay
overlayfs:/overlay       10.9G     60.7M     10.3G   1% /
tmpfs                   512.0K         0    512.0K   0% /dev
/dev/sda3               811.2G    590.8G    179.1G  77% /mnt/sda3
/dev/sda4                87.7G     90.1M     83.2G   0% /tmp/squid

I can't say if I have a device with or without enough flash space, so I ignored the second part of instructions. I know that I have plenty of space in my external storage and for packages and dependencies installations.

I am experiencing major router slow down and pages won't load after starting squid and applying firewall rule.

Look like storage space is not the only necessary thing. It seens that my CPU, FLA, RAM are also bottlenecks, of course. Just compared a ClearFog with my TP-LINK.