How should I make a transition from 2.25 turbo outlet (T3 Saab garrett internally gated) to 2.5 downpipe ?

If I make 2.25 flange to mate with the turbo should I also make tapered pipe transition (red lines on the drawing) or do not worry about it and simply weld 2.5 pipe on 2.25 flange ? I don`t want to affect performance.

How do you have your downpipes ?

 

you buy the flange with the 2.25" hole cut in it and weld the 2.5" pipe on around the hole :1

 

durrrr...

 

The time it took for you to make this drawing your DP would have been done.