Power management of HDD EON chassis?

Has anyone had any experience with the best way to manage any HDD plugged into the EON chassis yet?
I’m running a stock Pi 64 Bit LT with OMV, CUPS, PI-VPN and TVheadend all running well with each other, but when it comes to the power management side of OMV no luck!
Have tried a number of combination within OMV and they all seem to lead to the same result of the HDD stay running except for 1 that seems to constantly cycle its power in a controlled way that is, disable the PM and everything works well.
I am very much a newb to this so don’t bombard me with very technical answer as won’t fully understand.

Only issue to doing that is lose the capability of cooling the HD when needed!

You are absolutely right.
BUT, at least in my case, I´d much rather have the HDD spindown rather than check their temp and wake them up. I have 4 x 2.5 hdds (and an external one, 2.5 as well) but they are idle most of the time. I want to save power and most importantly, lower background noise at home. I only have media and some personal files on the EON. HDDs temps are usually lower than 30ºC with no active cooling and, when used, they usually do not spin up all at the same time.
Guess the final solution would be finding something to check the HDDs temps without spinning them up.

PS: and from what I´ve seen the current Argon config would also power on the EON fan if an external HDD (not inside the EON case) reaches the configured temps…