well... I've been REAL HESITANT to chime in here.... because of several reasons. There's reasons you keep seeing 1/4" recommendations and it's because of the way those sumps are designed... and the other's that don't know any better are sheep. (Not necessarily a bad thing. Copy success!)
Bottom line, if a baffle isn't going to be subjected to water pressure... if it's simply going to be a barrier that water slowly flows over or under... it does NOT need to be 1/4" glass. In fact, one of my sump's baffles that IS subjected to high flow and pressure is thin acrylic!
I constructed my sump from material available (ie: free stuff laying around).
So... the design of YOUR sump will determine if 1/4" glass baffles are necessary.
And I'm gonna guess 1/4" is not necessary