I’m remodeling a bathroom that’s finished out over an old garage slab. 2x8 joists sit basically on top of the old garage slab and plumbing runs between the joists and through the foundation into the crawlspace. I say this because it would be very difficult and require a lot of demo (including the floor and a wall) to replace the plumbing. The 2 inch shower drain leading into the P trap only has about an inch and a half of 2 inch pipe sticking out above the P trap. I’m using a Schluter linear drain and the fernco connection only reaches over about a half inch of that 2 inch pipe. First question is whether a fernco connection will be faulty if it only goes over a half inch of the 2 inch pipe. If I extended the two inch drain pipe with a coupling, then the fernco would be too long and butt up against the coupling before I am able to set the drain flat on the thinset. Would it be possible to use a “pipe extender that goes inside the current two inch pipe and extends the 2 inch pvc to the correct height? I’m asking because that will slightly reduce the inside diameter of the 2inch pipe for a couple inches. This all doesn’t really matter if the fernco connection will be successful with just a half inch overlap over the 2inch pvc. Thanks so much for your comments.