I have added a new subfloor to my bathroom and am ready to put some schluter membrane down on the floor before tiling. The old insert to my toilet flange will not come out. I am abte to get an asb 3 to 4" flange into the hole but it now sticks up about 1" above the subfloor height. This could be okay but do I need to get the old insert out? And how? What do I screw the flange into if I cannot? Any help would be appreciated. Thanks Kendall