Take the tub out, get the fiberglass kit, before you start cut the fiberglass cloth in such manner so that it covers the crack and also supports the rest of the pan, from side to side and at leasr a couple of inches up the sides a minimun of two layers.
Also get a coulpe of stif cardboard pieces of 1 to 1 and half wide that go from the area of the drain hole to the back.
Measure the hight of the pan floor to the actual floor of the RV and with plywood build a bench for the pan to rest on, it is a good idea to epoxy or paint this wood before bolting down.
Clean the bottom of the pan with wire brush, lay the first swatch of fiberglass cloth down and roll, now lay the two stips of cardboard down making sure that yo do not get any fiberglass mat or resin on the drain flange, if this happens you might not be able to seal the drain fitting, now lay the next piece of fiberglass on top of the cadboard and tuck along the edges so that there is no air bubles along the cardboard edges, roll and let cure for at least 72 hours.
Reinstall the drain pipe if taken apart install pan in shower enclosure connect drain and you should be good for the life of the RV.
navegator