Best answer by AjTrek1
In that type of set up (Play1/Play 5/Play 1) the Play 5 would essentially disrupt the stereo sweet spot created by the Play 1's in stereo pair. I don't even know if a name exists for an arrangement of that type.
Low end is set at a crossover point (say 50Hz or 150Hz for example) via a circuit board to send those frequencies to a specially designed speaker and send all others to the L/R front speakers for Mids and Highs. The speaker producing the low end can typically be placed anywhere in the room to achieve the audible or physical thump (if you like to feel bass) of those low frequencies.
A full range speaker such as the Play 5 cannot be adequately substituted as a low end speaker between a stereo pair. The EQ in the Sonos App is not capable of completely "erasing" the mids and highs of any Sonos speaker. That would require a mixing board and the ability to turn some of the speaker array in the Play 5 completely off.
In your arrangement you might hear the low end but it would sound very localized and not part of the entire setup. Moving left or right you would lose the low end on the opposite side. You'd be better off investing in a second Play 5 Gen2 and placing it in stereo pair with your current Play 5 Gen2; as many say in that setup no sub is needed.
You could repurpose the Play 1's and Play 5 Gen1 to another part of your home. However, you can always try your arrangement and if you like it...then problem solved.