I looked up the fields swg power vent, they show a 7" square hole with the 6" outer pipe going thru it. You should look up your specific model number to get clearances,but from what I saw they want 1" around where unit goes thru the wall. Pipe joints don't have to be sealed since you are sucking gasses out, worst is you may suck fresh air thru a joint. You should however put screws in the joints to hold things together, 3 screws per joint. I'm sure others will be along to help out. A lot of this is covered already you just need to use the search bar to bring up past threads.