Size range for halo setting

[Noodeloid]

Hello all! I wonder if anyone has experience in swapping out their centre stone for one of a slightly different size?

I have a cushion halo setting. The prongs are about 6.5mm apart, and the centre stone is between 7.5mm and 8mm. I have a gemstone now, but am looking at replacing with a diamond of a slighty smaller size. In your opinion, what mm range could I expect my setting to accomodate?

Pic for reference:

 

[DiamondBrokersofFlorida]

If using the same prongs, the smaller dimension and possibly .5 smaller. It might be possible to modify the center to take a smaller stone as well .

 

[chrono]

In general, you can go down 0.5 mm safely. Too small will allow the metal underneath to show so you'll end up with an airline gap.

 

[Noodeloid]

Thanks so much ladies!