Looking for a 3.5inch to 4inch adaptor/reducer

Hi, I'm looking to replace an old 3.5inch cast iron soil pipe with new uPVC 4inch soil pipe, but I cannot find an adaptor to suit? I looked at the McAlpine coupling with the rubber fins, but don't know if that would fit into the smaller cast iron pipe? I intend to replace the pipe from the ground up.... anyone know if the McAlpine adaptor can be used or if there is a better option or better way to do it?

Thanks

 

[ShaunCorbs]

mcalpine dc1 should fit or a time saver coulping

 

[AlexNIC]

mcalpine dc1 should fit or a time saver coulping

Would the McAlpine dc1 being 4", fit into the old cast iron base which is 3.5"...or would I have to 'cut' the rubber fns to suit?
Wouldn't have thought the time saver coupling would be suitable for 2x different pipe sizes?