neck yoke length

I am unclear on the terms you are using?  Double neck yoke?  Is perhaps a neck yoke with two jockey yokes (my terms – sorry).? or just a three foot yoke made for a team  (not usually refered to as a double neck yoke).   In that case the three foot neck yoke matches if you use a three foot double tree behind the horses.  In any case your yoke and evener should match or be close as they aline the front end and the back of the animals.  A martengale I think of as a harness with no collar and a breast strap for a horse pulling a light rig.  I might easily be wrong in this as it is not a setup I am that familiar with.  As for the two foot yoke; That may or may not go with the martengale and it sounds like a jockey yoke.

Peyton,  I didn’t modify your post – it just thinks I did!  Still learning, D

The use of jockey yokes (short – individual yokes) will depend on the type of harness you have.  A side backer or a D ring harness will use a short yoke along with the three foot yoke; while a belly backer will not.