Try LaBella HRS strings for higher tension at lower gauges
I tune to drop E on my 8 string, and I've been struggling a bit with string gauges. I HATE floppiness, so I had been rocking NYXL 9-80s to get better tension on the low E. It feels good but I was frustrated with the unbalanced sound of the .080. After some research, I took a chance on LaBella's 9-74 HRS set despite having no tension calculator or authoritative reference proving higher mass and higher tension at similar gauges.
I'm pretty satisfied with the results. The tension of the .074 feels similar to what I imagine an NYXL .078 would feel like, but it sounds so much more like a guitar string than a .080, a natural extension of the other strings. On the downside, the LaBellas feel stiff and are harder to bend than other .009 sets, but they're not as stiff as .010 sets. The wrap also feels somehow tighter, so the .074 feels even smaller than other .074s under my fingers.
I also plan to try Kalium, so my journey isn't over, but in the meantime I would heartily recommend LaBella for anyone looking for more tension on their 8 string. IMO it's a better option than going thicker.