Ikea hay rack?

Hello Happy Hoppers!! .. Guinea pig question here..

I've just ordered 2 of the ikea back dispensers, to use as hay racks (photo below)



I'm planning to turn them onto their sides and stuffing them with hay.. I've bought one for the bunnies and 1 for one set of my piggies, however, i'm worried about the guinea pigs getting their head stuck through the front holes? I'm going to be pushing the open end against the hutch wall so that shouldn't be an issue. Do you think they'll be okay.. How can I prevent them from sticking their heads through?

I don't know much about piggies I'm afraid but the holes don't look massive . It's blimmin fab for buns though!

They are great for bunnies but like Katie am not sure how they would work with piggies. I suspect the holes may be too big for piggies for this to be used without worry.