Yep, I would recommend altering a wooden playpen too.

When we moved from up north to a colder climate in the middle of winter we had to organise a barrier asap and didn't have time to shop around to hubby ammended out wooden playpen to fit around the fireplace and it works really well as we can just step over it and it take it down in summer.

We've just bought a gas heater for the coming winter and I picked up another wooden playpen on sale at Target for about $85 to make another guard.