I've built a 20M vertical dipole using two Hustler 6-BTVs mounted back-to-back about 40 feet high on a wooden mast. The vertical dipole configuration was chosen because my house and back yard layout do not lend themselves to the installations of a good ground radial system. The antenna resonates perfectly at 14.200 MHz but I'm seeing 2.3:1 SWR across the phone portion. I have a 1:1 balun at the feedpoint and a 14 turn coil of RG-8 coaxial cable wrapped around a 7 inch diameter fiberglass form. Should I move the choke balun closer to the feedpoint, or is this just normal for a trapped vertical dipole?

That SWR sounds about right for a trapped antenna, especially with two 6-BTVs. The total power loss is around 1.5 db on 10 meters, 2 db on 15 meters, 2.5 to 3 db on 20 meters compared to a non-trapped design. Try adjusting the trap positions slightly before moving the choke - sometimes just a quarter turn on the coils helps.

I had similar issues with my vertical dipole setup. The choke balun position isn't your main problem - it's the traps creating narrow bandwidth. Choosing one of the trap free antenna designs that are now available, in place of the Hustler design, could minimize the losses on the 20 and 40 meter bands.

For comparison, I tested my vertical against my hex beam on 17M. The vertical dipole usually has a 3 to 6 db higher noise level, compared to the hex beam, and produces signal levels that are typically 3 to 6 db less than the hex beam. Your SWR is workable - focus on getting the antenna higher if possible.