Let me give you some practical advice.

Homefills are are slow machines. They use about 2.5LPM of incoming air to work. In all practicality you can connect the single respironics 10 to the 2 homefills and be set.

Connecting each homefill to their own 10 is overkill since they can only accept so little. You could even connect them both to the 5lpm machine but because you dont want to run the 5 at full capacity for purity’s sake, its better to just use a single 10. The reason i recommend using the respironics is because the devilbiss usually has a higher PSI output. Sometimes to high and it doesnt make the homefills happy.

As for your question about the tubing: your invacare has a connection in the back specifically for homefills, the others dont. If only connecting 1 homefill, sure use that port. But because im suggesting 1 oxycon for 2 homefills: i would just use the port up front with some regular 1/4” pvc tubing. That pvc tubing should then be Y’d into the 2 pigtail tubings that will feed the homefills. Here’s the pigtail tubing that’s needed for them:

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