Installing wheel studs into modified brake rotor

[GTVeloce]

I am currently changing from four stud to five stud hubs and have a couple of questions. The car had previously been upgraded to vented rotors and brembo callipers and to work with the four stud hubs the rotors have been drilled to suit.
1) any reason why I can't still use the rotors once I install the original five studs? Balance issues?
2) should I use some form of stud locker to help ensure the studs stay in place?

Thanks in advance

[Duk]

I am currently changing from four stud to five stud hubs and have a couple of questions. The car had previously been upgraded to vented rotors and brembo callipers and to work with the four stud hubs the rotors have been drilled to suit.
1) any reason why I can't still use the rotors once I install the original five studs? Balance issues?
2) should I use some form of stud locker to help ensure the studs stay in place?

Thanks in advance

On 2 other non-Alfa cars I've done 4 stud to 5 stud conversion and 5 stud to 4 stud.
Neither car showed any noticable vibration as a result.

[GTVeloce]

Thanks Duk. My concern is not from changing stud patterns but from using a disc that now has three extra (unused) holes in it. Regardless, I have decided to try it and see how it goes. It's not the end of the world if I have to change it later.