I came up with a simple solution that works great.  Instead of trying to conform the liquid fuel object to the inside of the tank, I just used a box , tessalated the top surface and applied the Ripple modifer to that.  I hid the box under the tank and surrounded the tank with a concrete support structure.  Even tho the box (liquid/fuel) is larger than the tank, the surrounding concrete structure hides it.  Instead of using slice, I just animated the box up in the Z axis.  So simple I could smack my self.

Thanks for thinking so hard on this.

Kenn Macintosh