This is a complex problem that I am also struggling with. I also use NGC and my idea (which I have not tried yet), is to increase the size of the object radius when the frames of your object are between a set number.
Say your normal radius is : SetObjRadiusPro(5,5,5). Then, when you swing the sword (which is, we'll say, between frames 112-145), you may be able to do this:
player = 1
frame = object frame(player)
if frame > 112 and <145
SetObjRadiusPro(9,5,9)
endif
Then reset the radius at the beginning of your game loop. I don't know if this is a possibility, but may be worth a try!