How thick should the front baffle of speakers be?

Whatever happened to those things you would stick to the sides of your speakers to deaden them? Did those pass into tweak history? (I don't really care) Note that my current speakers, Klipsch Heresy IIIs, tilt back so anything placed on the top just slides off. Keeps things from gathering there.

Randy Bankert passed away a number of years ago. His front panel design was copied from the Zingali speakers that he had previously represented. Like many importers the manufactures always expect more sales and are never completely satisfied with the sales of the importer.

The thickness of the front panel should also be determined by how wide the front is. A large 16" panel will necessitate a stronger panel material. Narrow front panels not so much. Plywood is good, better then mdf. Alon  Wolfe went to plywood on his earlier versions of the Magic monitor. 

" wheres the proof "  Simonmoon is 100% right and that has been my experience too and measurable through REW and TrueRTA but you can't post results here to prove this because no pictures allowed.
  I had a set of La Scalas that had been damaged and I decided to replace the 18mm sides with 25mm Baltic Birch sides. You don't have to believe me but the perception of much lower bass was startling. What I was actually hearing though was bass without cabinet resonance masking it and it was a real eye opener. Since then everything I build with any area at all gets 25mm wood. Real honest wood and not MDF.

" Hi, The speakers that I own (Sonist-"Concerto 4") have two inch thick poplar wood front baffles.   I talked with the designer (Randy Bankert) and he said he tried a bunch of different woods before settling with poplar as it was the best sounding to his ears. "
  That's interesting. The old Klipsch Chorus speakers used  1" poplar plywood for the front baffle and I always though that was because it was cheaper. You pick up pieces of differing types of plywood or MDF roughly the same size and tap on them and the range of sound is pretty large so what that guy says makes complete sense. Those old Chorus speakers are my favorite among the Forte, Heresy Cornwall and Chorus.