Chosen Solution
I currently have an iPhone 6s and I was wondering if I can put it into an iPhone 6s Plus housing with a iPhone 6s Plus screen, I want a bigger screen and phone and just want to see if this is possible
Unfortunately this is not possible as the board of the 6s is completely different to the 6s Plus, along with the screen and other parts. Better off selling your iPhone 6s and buying a 6s Plus or newer.
