I treat the side tabs as decorative, I have not tried cinching them. I would imagine you could get 1/4"-1/2" or so on each side without deforming the pant too much. They hit me pretty much right at the belly button.
Eidos Brown Charcoal & Maroon Gunclub sportcoat with Maroon overcheck
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Luigi Bianchi Mantova Air Force Blue Polo coat
Vass F Last Dark Brown suede Chukkas