Taking bags into away grounds

Just seen on my ticket that bags no bigger than A4 are allowed into Portman Road.

I'm going on my own tomorrow so need some form of entertainment on the train so was going to take a book, headphones and maybe food for way back.

Ideally I'd take the above in a rucksack but last thing I want is to be told I can't go in with it.

Anybody got any experience with bringing a bag into an away ground?

Especially interested if you've tried at Ipswich.