ASUS RT-N12 VP with coocachilli or chillispot

Hi, I've this router with Asus original FW, I need to add autentication for guest's WiFi, the provider told me to load OpenWRT and install also chillispot or coocachilli, which took about 3MB.
Can I install them or 8MB flas are too few?
Thank you for clearing this problem

The RT-N12 has 8MB flash, why this warning?
I hope someone may help me here, thanks

Unless I'm mistaken, it still has 32 MB RAM.