I used the bulk head fittings and wrenches to tighten mine with no silicon or sealer and they seated just fine I too have my barrels cut long ways..I used the bulkheads foam washer on the outside and no leaks.... I found that a heat gun and a Plastic welding kit from Harbor Freight to be quite useful when working with the barrels...Just my take on it anyways....

Yikes didn't see the post was 3 pages long already so info probably out of place...I guess that's what I get for typing without my helmet on.....