Load your magazines to full capacity (7 and 8 rounds respectively) and let them sit for a week or so. Then, lock the slide back on the empty gun, insert a fully loaded magazine (8 or 7, whichever), and then sling shot the slide, or use the slide release (if you can.) If you prefer, you can drop the magazine and load it back to full capacity, so that you are carrying 8+1 or 7+1. You may have difficulty getting the fully loaded magazine in when the pistol is in battery, but after a while you should be able to do so.

Personally, I only use the 8 round mags, and I carry 7+1 in the gun, with two 8-round back up mags. If I can't get it done in 24 rounds, then I'm in more trouble than I can handle with one more round.