I have an 870 similar to yours, only mine came with no dimples, a 2 rnd extension, and an LE slide. I understand that yours will be subjected to little if any punishment; probably not as much as mine which currently serves as a trap gun at the range but afer a barrel switch adopts the HD role at home.
I also wish that I knew before firing the gun how easily that dang barrel clamp can loosen and mar the finish. Still, if occasionally checked and tightened it is fine; at least mine is.
Actually, I don't even use the barrel clamp since it is a PITA as frequently as I change barrels, which is usually twice a week, and it is easy to further mar the finish when sliding it off and on. Some would use it without the clamp, but I think that is foolhardy for the reasons Dave mentioned.
The Vang may be different, but if the factory extension is slightly off you can develop feed trouble.
If you haven't done anything about the dimples in your tube, you may wish to take a look at this.
http://www.aiptactical.com/How-To_Videos.html Look at the one on installing a 2 rnd extension kit. JD advocates drilling the dimples out and then using a dremel for deburring.
Anyhow, Dave knows infinitely more than me and you seem to know everything, so enjoy your retirement.