Michael, I wouldn't EVEN worry about doubles yet.
Here's why; I was also dreaming of doubles before I ever finished building my single tank rig. Last week, I finally nailed my bouyancy weighting. Now I'm having one devil of a time getting my trim right. I'll get so close to being spot on, then make one tiny adjustment and everything goes to hell. Yesterday I un-intentionally "perfected" the art of hovering upside down after making an "adjustment".
I guess what I'm trying to say is- focus on your singles rig for now. After you've had to move your weights and adjust your tank height 3258 times...if you are like me, you will be in no hurry to build a doubles rig!
Here's why; I was also dreaming of doubles before I ever finished building my single tank rig. Last week, I finally nailed my bouyancy weighting. Now I'm having one devil of a time getting my trim right. I'll get so close to being spot on, then make one tiny adjustment and everything goes to hell. Yesterday I un-intentionally "perfected" the art of hovering upside down after making an "adjustment".
I guess what I'm trying to say is- focus on your singles rig for now. After you've had to move your weights and adjust your tank height 3258 times...if you are like me, you will be in no hurry to build a doubles rig!