Help with configuration of custom parts ?

[pinarj]

When a valve of a measure in a pipe from his corrspondiente as I add no proplemas, but when I try to enter a valve less diameter in a pipe of larger diameter one standard valve and not the custom valvual, which I think it should be ingrega aggregate and generate reductions for coupling.
In the first image is ev no problems with adding valves in the second picture is that I want to add uan valvual smaller the pipe, the third is that the plant 3d valvual do not want to add, and in cuarat picture looks like I want it to look, if I do it manually can be done but I want it to just add the automatic valve in a pipe and the automatic reductions, desconosco generated as I fix this.

Thank you for your help.