Roof rack box ideas

What kind of storage boxes are people using on their roof racks? I have a prinsu rack which I mounted a Plano rifle case to. I got square U bolts that fit around the crossbars and drilled them into the case, and covered them with silicone from the inside. Water still got into it pretty regularly. The seal on the lid was pretty thin. Anyone have a better solution that does not involve drilling holes in a $250 Pelican case? I've seen the aluminum boxes but they are way to tall. Thanks for any input!

 

DAMN .... i got myself a plano rifle case too! no water yet not that I know off....

 

How are you going to mount it?

 

I did the same using 4 U bolts. I didn't use any silicon. I washed it many times. Haven't had any hard rain in cali yet.