on the 16, 28 and .410 forum, go to feb. 27 2016
there is a thread started by "The Woodsman" titled CZ Sharptail 28 ga.
he has a nice setup for a sling on a SXS
I would hesitate to solder on a sling mount before checking that the heat your putting on the barrel doesn't cause the solder holding the barrels and rib together doesn't make it all come apart.
the Thread is on pg. 4