Currently, for the 6" elbow duct to be centered correctly onto the range hood the elbow duct and the wall cap ducting must meet inside the wall. Which also means the joint where the elbow duct and the wall cap meet must be taped inside the wall.
What I'm trying to avoid:
If the taping happens inside the wall, then any time anyone needs to work with the ducting they will need to tear out a large section of dry-wall so that they can tape the joints inside the wall.
Options I've researched so far:
Seemed promising as you could coat the two ends of the joint and then push them together. However, everything I read about mastic indicates you need to also screw or tape the joint.
What if I could remove the wall cap?
If I could remove the wall cap I could tape 6" elbow duct to the straight ducting, then push the straight ducting through the wall from the inside.
Reattaching the wall cap seems daunting in this situation. How difficult would it be to get things flush? If I get the system all setup before taping so that it is flush, then reassemble it I think the problem is solved.
Main problem with this one is I don't think there's anyway to remove the wall cap! Maybe there's a better product I don't know of?