Disadvantages of cross breeding turbos?

[Likklekilla]

I would like to know is there any disadvantage to cross breeding turbos. That is like puttin on a bigger compressor with a smaller turbine housing. For instance those people who put on a t4 compressor with a t3 .48 turbine housing. Can there be ne disadvantages to such a setup and wats the worst that can happen? In some cases people can share there experinces with such a setup.

[Honda4VW]

hybrid turbo's are very common. I am sure you have heard of T3/T4 hybrids all over these boards.
Basically they allow you to have a quick spooling turbo with a large compressor to allow big CFM numbers