I have a main panel in my garage, with an existing sub-panel mounted right next to it. I want to add a new sub-panel at the opposite side of my house and need to run three #8 THHN and a #10 THHN into the existing sub-panel. There is an attic above the existing sub-panel and I can get to the top-plate to drill through it. I would like to minimize drywall repair. I'm trying to figure out what the best way is to run these THHN conductors into the panel. I'm planning to do this with a homeowners electrical permit, and want to follow the 2017 NEC.
I would be a tiny bit (41.3%) over 40% conduit fill if I put the 3 #8 and 1 #10 into a 1/2" FMC, but 3/4" FMC would be be best. I will have a junction box in the attic, so the total FMC run would only be about 5 ft (37" from the top of the panel to the bottom of the ceiling). I was hoping to attach the FMC conduit connector to the FMC and lower it through the hole in the top plate and feed it into the panel. But I would need to drill a very large hole in the top plate to be able to fit a FMC connector through it. I found these "Arlington 38AST 1/2" SNAP²IT Connectors with Insulated Throat" connectors that I think you can mount from the panel side, but they appear to be limited to 1/2" FMC.
Another issue is securing of the FMC. I think I need to secure it within 12" of the panel, which would mean opening up the drywall. Is there any way around this? I'm not set on using FMC, but it seemed like the thinnest wall conduit I could feed from the attic.
What is the best approach to do this with minimal drywall repair?
FMC run would only be about 5 ft (37" from.... Is it 5' or 37"? 5' = 60" and 37" is 3'1", so there's a bit of difference. I guess 37" is more "about 5 feet" than it is "about a mile", but... ;)