I use the squeakless wound Fremont Soloist low G with Martin fluoros on my Kamaka concert.
My recommendation is to avoid low G sets in general, especially the non-wound ones. When I first started exploring low G I absolutely hated it - I kept buying low G sets and the G was always boomy and floppy-feeling to the touch. Once I tried a wound string there was no looking back!
Another vote for Fremont Soloist Low G. I think HMS sells singles of them. I've never needed to widen the nut slot for them to fit.
I've swapped between fat fluorocarbon low Gs and skinny wound low Gs on my tenor with no issues with the widened nut slot at all. More of an issue on steel strung instruments in my experience, you can get away with it on nylon/equivalent instruments much more readily.
I use Fremont Blacklines and LOVE them. Ive got them on my Gretsch concert right now. I tried Aquila nylgut, Aquila reds and Oasis brights before the Fremonts and all were just "ok" on this particular solid Koa uke that is a little overbuilt. The Fremont Blacklines really rounded out the sound range and projected much better than the highly recommended Oasis brights for a solid koa instrument. The low G adds such a great bass drone in the background. The G string on this particular set is pretty fatty so I did have to widen the slot to accommodate it.
Honestly...not in a way most would but Im a diy'er lol. I used a narrow round file with a pointed tip. I put several layers of tape below the bridge on the body in case I slipped. I put the tip of the file at the top of the slot and then just used pressure to run the tip of the file down the length of it. Simple, quick and honestly, you cant tell that I did anything to it at all. I havent worried too much about using smaller strings in the future. I just double up on the knot at the end of the string and haven't had any issues and I change strings very frequently.
Cool, is the wound Fremont Soloist low G available online? And, did you need to widen the slot on the nut? Is it the one from HMS?
I'm starting to lean toward the wound Fremont Soloist low G single string because the nut doesn't need to be modified for a thicker string.
Has any one had problems going back to a thinner high g string after making the nut slot wider for a thick low G string?