[aerohead]

soften every leading edge that you can,especially around the top and sides of the windshield frame.Close all the gaps which allow air into the front wheels.An airdam which extends as low as the bottom of your lowest suspension member will give you a lot of the good a bellypan might.Allow some radius at the outer edges of the dam,or you'll have separated flow.Side body extensions including the front fenders which extend as low as the front airdam will allow air to go "around",rather than "through" the chassis.Don't do the grille-block until you've done these things,as you need to lower your cooling "load"first,or run the risk of overheating.As mentioned by other members,the hardtop will do you no good if you can't get a handle on separated flow in the front of the JEEP.If you can get the flow attached,the roofline can save you big time money.Model yours after the military version of the HUMVEE fastback.The flow will separate,and you can help that with a rear spoiler.You'll have a simple shape,easy to build and get on the vehicle.Rather than the dramatic upsweep,as depicted in your graphic,allow the bottom of the vehicle angle up at no more than 2-3 degrees,starting out,then further back,allow it a steeper angle to clear driveways,hill-climbing and such. Darin has posted a photo of CAR and DRIVER's Crisis Fighter Pinto article of 1974 in the blogs.Follow that lead on the JEEP and you'll be thumbing your nose at the gas pump.