As they say, everything in moderation. Have you weighed the gun recently? What about with all those shell holders populated? Do you have a proven and practiced method for actually using the holders to reload the thing on the fly?
Don't get me wrong; I like "tacti-cool" as much as the next guy. But, the gun isn't much use to me if I need a chain hoist and a week's notice to move it! For instance, my semi auto HD gun only has a six round saddle (which, technically, won't even refill the magazine) on the side and a simple Surefire G2Led light. (It's still a little heavier than I might like; with 13 rounds of 2.75" 00 Buck, it weighs around 9 lbs.)The shells are oriented so that I can use my forehand to either top of the mag or "cup" one around the bottom of the receiver and into the ejection port if the gun is completely "dry". It takes some practice, but it’s possible to load the gun without dropping the muzzle.
Bottom line, if you are doing this for fun or looks, you can do whatever you like. But, if the gun is meant for some purpose, you need to weigh the tradeoffs. After all, what's the good of having two (or more) complete reloads on board if the weight of the thing throws you off balance every time you try to maneuver it?