wreck the neck?

[Greg Ashton]

Lately I've removed the G string on an acoustic guitar and tuned it as an octave mando with an extra bass string as follows,tuned from low to high: D space GDAE. I prefer leaving the A string slot empty so I don't accidentally strike the extra bass D string. The question is, will this lead to neck warpage since there are more strings on one half of the fretboard?

[Luthier]

If you are using single strings (and it appears that you are) I do not think you will experience any twisting as you mentioned you are concerned with. #You may also wish to experiment with different string gauges to see which will give you the best sound under the required tension.
An accoustic guitar scale length is longer than that of an OM so you will have to take that into account as well.

Don

[Eugene]

Guitar scale is more like that of mando-cello. Have you tried dropping your tuning by a fifth and stringing accordingly? It could be interesting.

[Ken Sager]

I've restrung one of my guitars as CGDAEG (Fripp's New Standard Tuning). There's a local shop that carries bulk strings and I put together some custom guages that I like. I'm going from memory, but the guages are roughly:
C .058
G .044
D .032
A .022
E .012
G .009

The high G string can be brittle tuned up that high, but I like the effect. The other strings are tuned in 5ths, with a minor 3rd from high E to G.

Best,
Ken

I forgot to add that the total tension seems a bit lighter than a standard set of guitar strings. I adjusted the truss rod slightly and the action is perfect.