Body help/advice needed

in my opinion rod your better off welding the holes shut. take your time and keep it cool. ive seen glued in pieces and over time they have a tendency to show back up from the paint and filler shrinking. Just my opinion. my other concern is if your building a healthy motor the vibration may get to it as well. any seams that you are worried about use seam sealer there are several good brands. when it comes to bodywork there are many different methods. don't be afraid to try or you wont learn anything.