Sorry Marine...
Never mounted the side saddle on my M590a1...in fact, gave it away to a range buddy...found it wasn't for me because
I did shoot a friends shotgun that did have one mounted and found it not to my liking.
Not much help...but I didn't want your question to go unanswered...to me, it's just a matter of preference.
Thank You for your service to our Great Country...
Semper Fidelis Brother...