We have the large DP magnetic tank bags on both our SSS. I clean and wax the tank regularly plus am careful to keep the contact surfaces on the bag clean. So far, so good.
We’ve used magnetic, strap on and snap on contact free bags over the years. Each has pros & cons.
On the mag-bag, they are easy to attach/detach but must be kept clean.
The snap on, no contact bags don’t touch the tank but can be a real PITA to attach/detach. Several times with the Bags Connection snap on bag, the pull cord on spring loaded release came loose and/or fell off, which made removing the bag at a gas station in the middle of BFE a difficult and frustrating task.
IMHO, there is no clear “winner” so choose the one you like and manage the “cons”.
'17 SuperSport S, Akra Slip-ons, touring w/s, hard bags, etc.
'12 Multistrada 1200S Touring, full Termi., (sold)
'10 848 Hayden SE, full Termi. (sold)
‘04 ST4s, full Termi., PCIII (sold)
'04 BMW R1100SA BCR, Staintune, Ohlins