I just got a new semi custom rifle and unbeknownst to me at purchase, it’s got flush cups on the left side of the stock. I can’t say I’m a fan, at least not of the aesthetics. But maybe I can be convinced of the function. What’s the advantage? I hunt with a backpack on 90% of the time so it being flat on my back makes no sense. What about snugging into a sling to shoot? Any advantage there? Sell me on these things before I grind em out and bondo over em.