I have been wanting to improve upon my speed for a while and found a few ways which have worked for me (contradicts your weights Donny)
  • Elastic rope forcing my relxed arm out quicker than normally possible (sprinters use this when they get a partner to run ahead and use the elasticity to make their muscles move quicker)
  • Alternation between no and small weights while shadow boxing
  • Training to brain so that my hands don't "over run the brain", more like a drummers training.
  • Plyo training for arms
Elastic rope I think I have talked a lot about in pretty much every post I've talked about speed . But i'm sorry going to say it again, my hands get quicker even after a weeks worth of doing this so i'm going to keep saying it until you guys get onto it (like tabatas).

The hand weights like Donny said can teach you bad form, but to be honest I think this would only have a dramatic effect if your not correcting yourself in the process. Personally I do 20 seconds of the desired punch without weights, then 20 seconds with a small weight and then 20 seconds without weights again. Thats a set for me and done inbetween sets of the elastic rope. I think you have to make up your own mind with this one though as there are quite a few risks. Although I know the Soviets pretty much invented this technique and seemed to work pretty well for them.

I've recently been looking into how drummers train to improve their handspeed, because some of them have awesome co-ordination and speed I guessed I could learn something from them. Anyways what I stumbled upon was that they use patterns, which increase in speed as the exercise continues in order to trick the brain. I converted them over to jabs and straights in order to see if it makes a difference, only time will tell I guess, but i'm hoping it will make a difference.