I spent a good deal of time in the sandbox, party balloons are excellent for keeping everything out of your barrel. Rolls off like a condom when you are in your stand. Also keeps you from being hesitant to lower your firearm barrel first from your stand! (Safety, safety, safety!)
If you BZO for 100 @ 25m and are able to do so; get your true zero @ 100m. You will find the difference between BZO - TZO in the neighborhood of 2-4 inches.
Personally, my dope is set to 200 as my glass supports BDC -100/+850. A 200m zero has the happy coincidence of an initial trajectory cross-over at 50 yards, a distance available on almost all civilian ranges including many indoor ranges. This makes it easy to achieve a 200m BZO without needing 200m.... If 200m is available you can fine-tune the true zero at the real distance... At your earliest convenience!
Regardless of what you have your is dope set to, know where your rounds hit at less than your zero and know your hold under!