For minor cracks or holes Depoxi/Epoxy is best solution, in case of welding u wud lost the paint job and for propoer welding & strengthening quite a high area wud be affected then the apparent weak in current situation.
All Piaggio Owners some of you might be aware of the fact that Fuel Tank Lid of Storm 125 is having a flaw i.e. the water enters the tank through breather hole & Key hole, another flaw is the pot type collar for Fuel tank Lid which allows water to stay around the empty space & water drips in wen Fuel lid is opened. Apparantly they have implanted a metallic drain pipe through the tank for water exit but its orientation is not correct & it fails to perfom intended function. So practically the Srom 125 is more prone to Water entry then of other bike & such accomolation of water inside the tank definately cud leads to such issues. I have observed the issue in 2008, 2009 & 2010 & not sure if its still not properly fixed by manufacturer.