From personal experience, for a girl trying to record a male voice, two helpful things are:
1. Find your lowest pitch that you can do COMFORTABLY. Straining your voice is not helpful, and makes the voice you end up with sound very forced.
2. Voice act. Try to not just record at that low pitch, but try to make yourself sound like a boy at that pitch, if that makes any sense.
I'd actually recommend for boys trying to record female utau a variation of my two suggestions for the girls. That would be:
1. Find your highest pitch that you can do COMFORTABLY. A falsetto doesn't always work, although it can be helpful.
2. Try to make yourself sound like a girl at that pitch, or voiceact at that pitch. If that makes any sense. I don't know if it does. OTL
I have no idea if this was at all helpful, but. It's my 2 cents. XD
I'm female, but because I'm a contralto, my utau tends to sound rather boyish. (Or rather, in some songs I'll go "eep this sounds like a little boy! ;w; " while in others I'll go "what the heck this actually sounds like it might be a mature female??" and in still others I'll just go "**** it, I have no idea what gender this is OTL" So my solution for that was just to make my utau androgynous/have no official gender. o3ob I don't know if that helps you with your utau problem. ^^;