Smaller Screen Area

[retrocraze]

Hi Guys

Im new to the forum as I have recently made the move from Retropie to RecalBox. So far I love how well the games perform and I also love the retro shader that is available, the games look so much better!
One thing I would love to be able to do is have the games play in a smaller area on my HD TV, but in their original aspect ratio. Rather than have the games stretched to the full Y axis.
So that the games arent as stretched and look more like original size.
Is this possible? If so can anyone assist me with this?
Any help much appreciated.

Chris