I have two Optima red tops-double the amperage-and my Warn 8274-50 has been hooked to the side terminals for years. I winch all of the time. Not because I'm stuck, it's because were climbing up stuff that is so steep. I also have pulled several vehicles up stuff, out of sand, mud, and snow. I have yet to have a problem. My friend who supplied the batteries sells batteries at Standard Batteries. He hooked everything up with huge welding cable and crimp on ends. Maybe the dual setup is why I haven't had a problem? 
Saw it first hand that time and was made aware of another person having the same happen. Now we were on the verge of stalling that winch double lined so he was big time stuck. I think the 9k warns are pulling like 400 amps under full load. Not sure on the 8274 but the 8274 is a strange one. I have seen them out pull plenty of winches rated higher and seem to do it with less effort. I think that winch is underated.
4cylinder toy that fires off quick...may never be a problem. Dead truck trying to drive it out of a hole on the starter..........
