single vs double adj. LCA's
 

what is the advantages comparing a single adjustable LCA vs a double adjustable LCA for a drag setup?

Doubles can be louder and rougher than singles because a double has rod ends on both ends. Singles are typically rod end on one end and rubber or poly on the other end.

But neither will hurt your DD ride, it's all about how much noise you can handle. I have single adjustable and the noise is fine. However noise is subjectable to each person.

the thing im curious to is what is the tractional advantage with a double compared to a single adjustable? i understand you adjust the control arm shorter or longer to keep the launches straight, btu i dont understand what the second adjustment would be for? or is it just a finer adjustment towards keeping the launch straight?

you can adjust doubles on the car. you have to remove one end of the singles to adjust them.