Hi, I bought a used ES 339 Pro about a week ago. It still had all of the original stickers on it and looked like it was fresh from the box. What a fantastic guitar! Great sound, easy to play, nice split coils, etc. However, I have only been playing for less than a year and have learned to play on an Ibanez Prestige RGA321F, which is a tremendous guitar as well. About 6 months ago I started to play, and even practice, at all times standing up using a guitar strap . On the Ibanez, it balances perfectly with a strap on it and is flush with my body. It also made me learn the fretboard and to play without looking over the body and neck that I found I was tending to do while sitting down to play. Now, standing up to play is easier to me than playing sitting down.
When I placed the strap on the ES 339 I found that the strap button on the back of the neck caused the guitar to tend to want to flop over and fall away from my body. It does not hang correctly and is not balanced properly with the strap attached to button on the back of the neck and the one at the end of the guitar, at least to me. There is no comparison in balance and comfort - the Ibanez set up is much, much better. I could "hold" the ES 339 in place to prevent it from wanting to flop over with my right forearm on the body of the guitar, but I found it distracting, annoying and a definite disadvantage compared to the Ibanez, which has the guitar strap attached at the upper horn like any other Strat-style guitar.
For a fes days I have researched the subject, called Epiphone, etc. and then created my own solution to move the upper strap button from the back of the guitar to the upper horn. The wood in that area is only about 3/16 inch thick - not nearly enough for a strap button. Epiphone/Gibson should, in my opinion, build the guitars with a block of wood in that upper horn so that people like me who have a problem with the way the guitar balances (or fails to balance) with the strap button on the back can simply move it to the horn. I have seen where people have tried to insert wood pieces and glue into the horn through the F hole, or drill a large hole into the upper horn and try to insert epoxy into the horn with the guitar upside down. My solution was to insert fiberglass epoxy resin and a few pieces of fiberglass into the horn with the guitar upside down through the F hole. I taped off the guitar to protect it, used a piece of hose about 10" long with a funnel on it at the end to place the resin into the horn, and then placed the fiberglass pieces into the resin using some long stiff wire. I used about 2 or 3 ozs. of resin. The resin adheres tenaciously to the wood, strengthens the entire horn, and sets in less than 5 minutes. It gets warm too while it sets. I kept the guitar cool with a cool pack from the Frig. In 10 minutes, the bottom 1/3 of the horn was filled with hard fiberglass, which not only provides more than enough material to firmly and securely hold a strap button, but it makes the entire horn stronger than if Epiphone had installed a piece of wood in there at the factory. The strap button if very firmly attached to the stiffened horn.
The button hole was drilled in the horn at a slight angle so that it is 90 degrees to the strap while standing. The strap bottom was installed and I used a thin hard rubber washer under the button instead of the limp factory felt piece. I installed a very small stainless screw with a flat head in the hole at the back of the horn. It looks like a "factory" screw, but It is not even noticeable. I may install a small mother of pearl button there eventually.
All I can say is "What a difference. What an amazing difference." The guitar now hangs correctly, balances perfectly, does not flop over, feels very secure, lies flat against my body, and I am free to move my arms anywhere without worrying about the guitar wanting to flop over or flop away from me. Perfect. Epiphone, are you listening?
Disclaimer - I am not suggesting that anyone do this to their guitar - this was my project, my guitar, and my solution. I just wanted to pass this information on. If you do not like the way that your ES 339 flops around or wants to fall away from your body with the factory strap button locations and want to fix it, then take it to a good luthier!