BALLAST...on an airframe (any flavor) that is designed around one of the "beefier" engine packages, when one puts on a ZDZ of comparable power, the NOSE gets lighter (not bragging, that's JUST THE WAY IT IS)....so...on a new project, if you need a handy 8 oz of airborne ballast that makes sense, and doesn't add more than planned to the all up weight, just divide the fuel between a CG located tank, and the header tank. Have the CG tank sized for your "normal" burn, and the header tank sized for the correct "ballast" value.

For example, my 12 oz Dubro tank with gas in it weighs exactly 11 oz. I don't use 12 oz of fuel in my typical flight, so the MAIN tank of 16 oz becomes the primary supply....and unless something REALLY ugly happens, I never start burning down the header tank volume.

It's just about ballast.