I like the adjustable vacuum secondary from Quick Fuel. Seems like it would really simplify the secondary opening since it adjusts rate and timing of the secondaries. Has anyone tried it on their carb? Here's the description from Jeg's. I tried to post the image too but don't know how.

Quick Fuel Adjustable Vacuum Secondary Kits Adjustments made the easy way.

These Quick Fuel adjustable vacuum secondary kits will allow you to adjust the vacuum secondary to change the timing and opening rate of the secondary. They are made of billet aluminum and feature a polished finish.

if this is the one with the big screw head in the middle tht you turn to adjust tension, I've heard from a 2 friends that they leak around the threads

While I haven't heard good or bad about them, I wouldn't spend the money on it. Once you set it right, your are done with it. So, just get the springs kit for like $5.00 and spend 1-2 hours of tuning with it. Once you find the spring that works with your combo' you are done, end of story.