Jim, what you have said is true, antimatter does have normal mass hence would weight the same as normal matter on earth. But the graviton is what causes an object to have weight, so the antigraviton has the opposite effect on space and time. So in effect would push an object away from any massive object such as the earth.
But this is getting too indepth now and such a device is likely to weight several hundred tons.

Im getting a new tent for Christmas, one that is easier to put up and that doesnt leak, as people who have attended some events this year can vouch for.