air lock

[tlkbear]

Hi I finaly got all my stuff together now and i noticed my air locks are to small to fit in the 6 gal carboy, can i use a larger cork with a small hole to fit the air lock in? or should i just make a 5 gal mash and put it in
two 2 1/2 gal jugs? thanks for the input. btw im going to make a gerber rice mix if that matters? also 1 more question im makeing the 5 gal like i said this is my first run i was going to do a 2 1/2 gal sacrificeal run in a 5 gal pot,
is this enough or do i need to doa full 5 gal sacrifice run?