You guys are right. Clearly outlined in the rule book:
Page 43:
All equipment should be so placed that, when wearing an open concealment garment with your arms extended at your sides and parallel to the ground, it can NOT been seen from the front, rear or sides. Your concealment garment should be practical for your environment and loose enough to allow easy movement. Competition only garments are prohibited. Competition only garments are defined as: vented or mesh vests that allow the firearm, holster, spare ammo or ammo carriers to be visible when standing normally, artificial stiffeners of any material (other than standard laundry starch) used in any location, use of chest pockets, specially-made pockets or any material inserted in pockets or around pockets to keep the pocket open for stowage of partial magazines after a reload. Garments that are considered “competition only†will incur an FTDR. See “Proper Magazine Retention†in the Glossary for further details.