Not for me....
We bought a quantity of sidesaddles, and they were attached to working 870 LE guns. I took mine off within a couple of weeks.
For me, the sidesaddle obscures/covers, the very point where I grasp the shotgun in a common "trail" type carry, right at the receive junction w/ the bbls. I found myself using the shoulder sling to carry the gun even short distances 'cause I could not grasp in the usual fashion. Since I carry the gun more than I fight w/ it, is seemed an awkward accessory.
It would work better w/ the gun on some type of tactical sling or fighting sling, suspended in a ready position across the chest.
Many of the guys like'em, and they are fast. Guys that have worked w/ them are quick to top off the mag tube, etc.
I'm a big believer in having reloads available on the long gun for fighting shotguns and carbines, and have same on a utility scout rifle as well. You can grab the gun and go and have a reload on board. No pouch, rig, or belt to remember or forget, and loss of time getting into same. Who responds or patrols w/ long gun ammo on their person routinely, ya carry enough stuff already, so........
I took the backer off the side saddle and screwed the plate with the shell clips to the synthetic stock of my shotgun, in butt cuff fashion. Works great. Not as fast as ammo on the receiver, but fast enough. The ammo on the butt seems to offset the weight of the loaded extended mag as a bonus.
Plus...my spare shotgun ammo is where my spare ammo is on my carbine (Blackhawk butt pouch), coach gun (handmade leather loops), and savage scout (elastic cuff) so there's some commonality in training and gear.
There's an outfit that makes such a cuff w/o vandalizing a side saddle, but the sidesaddle was on hand and wasn't working out for me, so I rigged it.