improve open fireplace efficiency/radiance with iron basket/back

I know this has come up before but I'd be interested in the latest thinking. I have a fireplace in a new extension on my house. It has a one piece stone fireback , I'd guess about 12" wide at the back , opening to 18" wide at the front. I have a simple basket in it and burn logs.
I wonder if anyone has any experience or views on increasing the amount of "iron" close to the hot center to increase the amount of radiated heat ? I know it was common to use a cast iron fireback to improve radiation and prevent damage to the fireplace brickwork at the back.
has anyone found or even built a basket/back that radiates more heat forward and hence looses less by convection up the chimney. I was thinking of a basket with integral cast iron back, maybe even some modern thinking on increasing the forward surface area with thanes ?
I asked this question of my local fireshop but all they suggested was removing the whole existing back and replacing it with a cast iron box with ventilation flaps which convects more into the room but at a cost of 500 plus the incovenience.
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