Right now I have a 4" PVC pipe coming out of the concrete floor about 8" then capped (fully concreted in). From what I have been reading, I could get a flange that will sit (and be glued) inside this. Should I do this first, securing it to the concrete floor with TAPCONS, or do I leave it as is, lay the floor around it, then cut the 4" PVC flush to the floors finish grade, then seat the flange in it. If I do the second option, do I need to fasten the flange with TAPCONS (through the laminate) for stability?