I generally keep my 25.5" scale guitars strung with 9-42 sets and my 24.75" guitars strung with a 9-46 set, and all of them in E or Eb tuning. I have a country gig coming up that I need to play some tic-tac style parts so I want to tune one of my guitars A-a.
Normally, the solution would be to buy a set of baritone gauge strings and be done with it. However, I'm trying to avoid doing any nut modification to accommodate this because after this gig I'll go back to normal strings. Are there any suggestions for a set that would be a balance between being heavy enough to downtune a ways, but also not so heavy that I'll have to totally modify the nut to do so? Keep in mind, I like playing with small, floppy strings anyways.
I've not tried them personally so don't take my word for it, have you looked at the Dunlop heavy core strings? I think the biggest they do is a 54 or a 52. The thicker core means more tension against a string that has an average core. I'm not sure how much lower you can tune it though but I can MAYBE guess at about B with decent tension but it might go lower or it might not.
They are probably cheap so you could just grab a set and go for them.
Or you could try the DR Drop-Down tuning strings.
Again, I haven't tried them and they are a little more expensive than average strings but if you don't mind spending for experimentations sake then go check them out.