I personally would not use 24 awg solid core wire because it has severe limitations on high frequencies. I first went through the whole solid core cable phenomenon in the mid 1980's when a company introduce a cable called dnm solid core 26 ga for interconnect and 22 ga for speaker cable, it was very good and started me off on a career of cable design which in the end got me a patented cable that actually works, can't say on a proprietary basis what it is, but it isn't 24 ga. He would be better off , by far, and I'm picking a number he can manage based on my personal experience. It will be a magnet wire which means each strand has a poly coating on it so each strand will never oxidize or deteriorate and give him 10 times the performance characteristics of 24 ga.
I would choose for him to use 16 strands of magnet wire of 38awg wire in a twisted configuration. 38 ga is big enough for him to barely be able to manage but will result in a much more refined , detailed sound. that is 16/38gauge magnet wire, but solder flux must be used to remove the polysol 155 coating from the wire.
If he follows my advice I would be really interested in hearing his opinion of the results. I already did just that, 25 years ago, doesn't have anything to do with what I'm currently bringing to market via a high end company on the west coast, but hey,you've got nothing to lose.
Bay Associates sold me some wire years ago , you may have some luck with them and here's a link
Bay Associates - Litz Wire
btw, I have no relationship of any kind with them, just some fond memories of me haunting their warehouse
Interconnect probably.
