Being curious, I put the new drum in the stock to see how it would feel. Well obviously you won't be able to fire it the same. Unlike the "clips," that go straight down, the drum goes left and gets in the way if you're right-handed. So why not just turn the drum around?
Well if you had never noticed these guys (in green):

By tailschaser, shot with SPH-M810 at 2009-08-15
Those little nubs keep the clips from going in backwards. Well when you shave them off like in blue, they can go in backwards. However, being as drum and the fact that it's heavier, the drum will fall out due to the lack of a hole for the clip lock. So let's make one.
Get your dremel or saw or whatever and make sure you're cutting directly across.

By tailschaser, shot with SPH-M810 at 2009-08-15
If it looks like that, then it should work now.
Here's what it looks like in a LS:

By tailschaser, shot with SPH-M810 at 2009-08-15

By tailschaser, shot with SPH-M810 at 2009-08-15
And in the Raider:

By tailschaser, shot with SPH-M810 at 2009-08-15
So now we can carry 70 darts and still feel confortable in either hand.
By the way, the gun's shoot the same in either direction.









