Yep, it's totally secure even w/o the bottom bracket! Although it doesn't seem to block a huge amount of wind, does it?

 

Having some experience with drilling using hand drills and and drilling machines I doubt that when using a hand drill that the hole ends up the nominal drill size in diameter. Best chances are with a new drill, using a drill that has been hand sharpened all bets are off.
Always work up to the final diameter using smaller drills to start that way you can see if you are still on centre. If you have wandered off centre for some reason you can use a round file to move the hole back on centre and then finish the hole.
There is not much point in having the hole the correct diameter when it is obviously off centre.