Assuming the new lugs will cover the other holes then there's no reason you can't try it.  Use some blue painter's tape to cover the areas you need to measure and cut.  Measure where the new holes need to be.  Check-it.  Double check it.  Triple check it.  When all is good, the best drilling method is to place the shell on it's side and use wood blocks at the base to keep it steady.  Use a drill press and a level to make sure you're drilling is perpendicular and straight.  Hand drilling may work, but it's risky.  Tap a pilot hole first then use the regular bit.  Tape the bottom side and drill into a wood block placed flush with the inside of the shell.  Easy does it!  That should do the trick.