hi! I have the regular (not royal) x prong e-ring and I bought the matching curved band. I wore it for a while but I did not like it. It spun around and drove me nuts. I did not want my rings soldered together though. I bought a band from e-weddingbands.com, their comfort fit 3mm band. (not the light, not the heavy, but the regular comfort fit.) It works perfectly and I love it! There is a tiny gap between the rings but it does not bother me at all. I also have a very thin pave band from Signed Pieces that I wear sometimes as a wedding band but usually as a RHR but it works OK with the x prong.
Hope that helps a bit. If you look at my past threads you can see pics. Ellen also has the x prong with a 3.5 mm plain stuller band and it looks wonderful.