I'm just here to state the obvious... Hope you don't mind :)
You might not need to take up 8hp with Passive mults unless you really don't want to use Stackables or 0hp floating mults, I have 1x 4hp 4x4x4 Manhattan Analogue passive mult and thats usually more than I need.

Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.

https://youtube.com/@wishbonebrewery