Vetus Exhaust

[Zai]

I haver a Merry Fisher 655 with a 105hp Yanmar.
I would like to change the wet exhaust. The current exhaust is a VETUS plastic waterlock type LP75. With the boat purchase I recieved a new exhaust in the box. When I opened it I found that it was the next size up (105mm instead of 75mm)

Can anyone think of a reason it would not work to just weld a couple of adaptors in stainless or aluminum?

Any advice?