Has anyone had any experience welding plastic parts (like bumpers etc)? There are kits available that look to have a glorified 40 or 80 watt soldering iron and plastic filler rod, do they work well/worth the money (such as this one http://www.autobodydepot.net/scripts/depot.exe?pgm=plstweldgate.bbx )? Alternatly should I look into what tips I can get for a weller soldering iron some plastic rod and have at it (I figure the oxy accetalene would be a bit much)?

Looking to fix a broken bit on the bottom of a 92 W124 bumper. Looks like the previous owner wasn't too careful with curbs, one of the ribs is cracked through.

Related subject - what is the best way to get a white paint scuff off the black plastic bumper insert?

Thanks
Paul