Plan9port's implementation of fltfmt.c seems different enough to me that it isn't possible to simply take the fix from there and add it to plan9. Perhaps I'm missing something.
The g verb already acts differently in plan9port and native plan 9: print("%g\n", 0.1) prints .1 in plan 9 and 0.1 in plan9port. I don't why they're different, but the former behaviour is unfortunate for the native port of awk I am completing (started by boyd). Others are of course welcome to come up with fixes for this problem.