Well, the check valve thing is going to take a while, so I switched to remaking my vent lines. Here's attempt #1 for today.

Unfortunately, the last bend was too close to the end of the tubing. I tried flaring the tube before making this bend, but my bender deformed the flare. That's OK...the odds of this line fitting perfectly are slim to none, anyway.

Attempt #2. You can see that the downward leg of the tubing has been extended. I also shortened the vertical section another 3/8 inch to allow better clearance for accessing the upper engine mount bolt.

With some Adel clamps holding it in position, it looks like it should fit pretty well. I just need to trim the ends a bit.

About 3/32 off the horizontal leg...

...and about 1/2 inch off the vertical leg should do it.

With the ends trimmed and flared, the vent line fit very well except for right near the lower weldment gusset. There's only about 1/16 inch clearance between the line and these rivet heads. It's probably enough, but I think I'll make a slight design change to allow more clearance.

Attempt #3. Much better!

Some time later, I made up a mirror image for the left hand side of the fuselage.

Oddly enough, the horizontal leg needed shortened about 1/8 inch. Weird. Well no problem since the folks that make tubing cutters put these handy grooves in the rollers to allow for cutting off just the flare.

Left side done.