This invention by Travis works great, and the video was easy to follow.
By simply taping the 60mm fan between two 2" PVC adapters, I save a little bit of space - and a lot of the time which would have been necessary to trim the fan (to fit inside the rubber tubing segment). The Tape I used is 1/15 aluminum 3M "Cold Weather" 181A-P, 181B-FX Duct Tape (product number 3340). This is not normal "duct tape", it is thin and doesn't flex, and it WON'T loose adhesion like the not-code-compliant cheap stuff.
Unfortunately, my "big box store" did not have any 2"x1" adapters. My PVC pipe segments will only be 3/4" size, creating a lot more resistance to airflow. If it doesn't work OK when I install it, then I'll need to buy two of the bigger adapters online, and redo the pip segments and elbow with 1".
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My Installation: Travis was able to pull the level indicator and swap it to the other mounting point (on the left side side, opposite). That change made his PVC segment short and clean. I spent an hour trying to both "press out" my level indicator (from below) and "pry out" the darned thing from above, but I was unable to make it budge. Instead, I installed a much longer (and uglier) pipe from the left side mounting. I also lacked a proper adapter for the mounting hole, and sealed my connection with more 'duct tape'. It doesn't look good, but it works pretty well.
In a second surprise, the power input to the existing fan switch was actually the purple wire. When I looked it it (in a hurry, and to lazy to pull out my DVM) I thought "Well of course, they used the a black wire on the 12V source, and the switched wire to the fan is the purple."
Nope.
So my new fan is currently switched by the old fan switch. That original switch (for the other fan) was also built with the "on" position backwards and down, reversed from the label. And so - while leaving my new switch on all the time, the time, my new switch is simply an indicator light for both fans, which run together. This would be easy to fix, if I want them to be independent in the future. And the old fan is quite noisy, you don't really need an 'indicator light" to confirm that the switch position is backwards.
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The real test? a 3-day boondock is coming up next week. I will post another "real-world performance" reply, with (ahem!) genuine odors, after that trip.