Jones, hope you don't mind me jumping in here. I have never seen a slide fail. I have seen the stop get knocked off by nocking the arrow upside-down. (the stop hits the rest)I have seen them shot into grass roots that held them so tight we could pull the boat over obstacles while trying to getthe arrowout.
As far as tension, the weight of the arrow is generally enough on a spincast. If not, you'll quickly learn to use the thumb and fore finger to hold the line while you reel with the other hand. If there is excess slack line, it can get tangled in the spool, some tension will prevent that.
If you are going to use safety slides with a spincast reel, I strongly recommenda rod extension. It will keep you from drawing the bow w/o pushing the button. If you don't push the button, bad things happen. All of which end with much loud cursing. Been there...
Good luck.