How can i have a symmetrical and smooth blend??

[Hasti]

Hello everyone. I want to connect two surfaces with blend. Imagine the two surfaces are symmetrical in the Y axis. But the blend result is not. (the blend lines are not symmetrical also the shape corresponding to Y axis).How can i solve this problem? I tried adding couplings but it didnt make any differences. attach the pictures here

 

[MrCATIA]

I would think you should get a good, symmetrical Blend surface, if you apply Supports and Continuity. Which options are you using?

If you want to try other options instead of Blend, a Multi-Section Surface should work. Or, you could just blend one side by cutting the boundry curves, and then mirror that surface.