Low G string set on vintage Martin Soprano?

Will using a low G string set on a vintage Martin Soprano cause undo
stress on the bridge or top? Prefer actual users rather than theoretical
speculation.
Thanks so Much

The tension of the low G string should be if anything lower than the tension of a high G, so no.

But the nut slot for the G string might well be too narrow for a low G, so would have to be filed wider (and filled and re-cut if you wanted to go back to high G).

One thing to consider is that the physics of strings means that a low G might not intonate properly or make a balanced sound at soprano scale. To get decent intonation and tone the string needs a minimum tension, and at that scale length this would require a thick string. But if a string is too thick in proportion to its length, it doesn't intonate nicely - a common effect would be that the lower notes have a slight wah-wah effect, while higher notes either just thud or are out of tune. So low G soprano strings have to compromise, and are neither thick enough nor taut enough.

If you've tried your choice of strings on another soprano of the same scale length and like the way they sound and play, then no problem. If you haven't, it would be worth doing so (or finding someone with a low G soprano of the same scale to check this out). Widening the nut slot on a vintage Martin and then discovering your low G strings don't work for you would be sad, to say the least.

Chris makes great points there. Also, Philip, I recently got a Martin S-0 soprano, and I noticed in the "Care and Feeding" handout that came with it that the (higher-than-standard) "a D F# B" tuning is recommended (re-entrant). I'm betting this would exert greater overall tension than your intended GCEA (linear, low G) tuning, and the S-0 has handled it beautifully so far. I always have this concept that a uke needs a few days to adjust to its "new reality" before it really settles in and cooperates with the player, so give it some time!

I have a luthier built vintage Martin concert copy that right now has a wound G on it as part of a fifths tuning set. The tension is way too low and it plays and sounds terrible with that small Martin style body. I shudder with the thought of doing that to a soprano. Stick with re-entrant and leave the low G for tenor sizes and larger.

Oh, that's just wrong in so many ways...:shaka:

As you prefer actual experience to speculation, I have a low G on one of my vintage model sopranos that works just fine. It is well balanced and the intonation is fine. There is no issue with excess tension and this is a very lightly built ukulele. I was encouraged to try it by Sam of Kamoa ukuleles in Kapaa, Kauai and is a big proponent of low G sopranos.
Brad