Yea, lots of guys have made the centerline tanks functional - a buddy of mine put a round duBro tank in his F-15 centerline tank and he could fly it with it on or off. When it was off, the place where the centerline tank plugged in just became his normal tank vent (where he plugged in his overflow tank on the ground) and when it was on, the tank vent was on the side of the centerline tank.

Its not really a safety issue, IMHO, just make sure that the tank mounting is secure. Easy enough to do...

BTW, Global Jet Club used to sell a kit to do that for a 1/8th F-16, but I can't find it on their website right now...

Bob