I refuse to weld gas tanks any more. Its not worth the risk to me.
Do as you wish. Have the tank steam cleaned out by a radiator shop before cutting it open. Purge the tank with Co2 or welding gas.
Look closely at the pin holes. The area is usually bigger than you think. This can be repaired with a good two part epoxy like 3M Structural adhesive available from Napa and other places.
Can you put .023 wire in the Miller 211? Do you have C/25? Can you weld thin sheet?
Good luck, Take pictures
2012 R1200R !
2000 R1100RT (parts for sale!), 1976 R75/6,
There is a seat for everyone.