Some clubs, like Boro have a clearly defined policy as shown here:
http://www.mfc.co.uk/page/fans/flags-and-banners
It reads in a similar way to that which we were so forcefully told prevails at the Ricoh; but to an extent the debate there is the thoroughness in which it is decided to enforce the rules when it suits those empowered to do so.
I can't see anything similar on the Reading site, so I'd suggest mailing their Customer Services team for clarity ahead of wasting your time, or getting involved in something you'd rather avoid. Contact details as per the link:
http://www.readingfc.co.uk/page/CustomerServices/0,,10306~1064134,00.html
If you get any feedback, you could perhaps copy and paste it here to give clarity to anyone else interested