how to caulk a diverter tub spout with a 1/4" gap with no backing

In my home I have a single piece shower / tub fiberglass unit... something like...
http://www.lowes.com/lkn?action=productDetail&productId)581-15728-326032AL00
The problem is that the pipe for the diverter tub spout is not perpendicular with the shower wall, and so when I screw on the spout, I have about a 1/4" gap at the top of the spout, and the bottom of the spout is flush with the fiberglass tub.
The spout looks like...
http://www.plumbingworld.com/images/als-1011-2010.jpg
Unfortunately, the spout is one of those cheap ones that is hollow metal. And so there is only a sheet of metal at the top of the spout that goes perpendicular to the shower wall, maybe 1/32" thick.
Also, for some reason there is a round sheet of plastic that goes between the spout and the shower wall. Which creates yet another complication for caulking. The plastic looks like it is to keep water out of the hole in the fiberglass that the copper spout pipe goes through.
[diverter tub spout][round plastic sheet][fiberglass shower wall]
Does anyone have any suggestion for how I can properly caulk this spout?
My current plan is to:
1) tape the plastic sheet to the shower wall using blue tape.
2) caulk the gap with clear silicone (the gap has no backing because the faucet is hollow)
3) let the caulk dry (maybe apply a second coat)
4) caulk around where the plastic sheet meets the shower wall
I have now begun to think that maybe I should glue the plastic sheet to the shower wall, and then do (1), (2), (3), and (4).
Unfortunately this is a new home I purchased from a tract builder and so I do not have any installation instructions for the tub/shower unit.
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If this is a new home; why is this your problem to solve? Let the builder take care of it.
That said and assuming you still need help; here is an off the cuff solution. Spray some minimally expanding foam into the hollow spout through the 1/4" gap, allow it to dry, trim off the excess and then caulk the darn thing. No I have never done this or seen it done but it might work.
Colbyt
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It was a second bathtub/shower that we didn't use until after our 1 year warranty period. Honestly, I would scared to let this builder back into my home to sweep a floor, let alone fix something they did poorly to begin with.

I was thinking about that.
I am also thinking that part of the problem is the big hole around the copper pipe that goes through the fiberglass tub, and so I'm thinking that there might be some standard way to seal that hole so that water cannot flow thru it if the seal around the spout fails, but I'm still not sure what to use to seal the hole (gaps): about a 1" gap around the pipe. I've never used plumber's putty. Does anyone know what the typical way is to eliminate these prefabricated gaps in fiberglass tub/shower units?
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If possible get a flange that fits over the 1/2" copper pipe, probably with a 3/4" or 1" hole for the fitting, and glue this in place on the tub. The outside diameter will have to be smaller than the inside diameter of your spout though, or you can make the flange part of the "design" if it's chromed.
Cut off part of the copper pipe and add another piece to make it 1/4 to 3/8" longer. Then the tub spout will fit correctly. This would be best since you don't want water getting behind the tub. This isn't that hard since you won't be working on copper pipe that normally has water under pressure in it.
Find anotheer spout that will seal to the tub with the 1/4" difference. Not as easy, but different spouts can have different setbacks.
charles
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There is no pre-drilled spout hole in a new tub. The installer drills the hole. I usually drill a 3/4" hole for a 5/8" pipe. A bit of silicone seals the rest.
But I have never had a problem with a spout not seating properly. Any gap is usually at the bottom where it should be. Bet the butt hole ran straight copper with no threaded connection between the faucet and the spout except for the stub out. It should have a secured shower flange securely mounted to a board inside the wall. The darn thing may twist off in your hands when you try to replace it which someone will have to do someday.
BTW the is no limit on warranty in most states where a trades person does something they know is improper.
Good luck.
Colbyt
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