I think it will work fine with a little JB wield in the wire channels. I was going to buy one once. Instead I decided to use the DO-IT slingshot mold. The larger one makes .44 and .50 cal. balls and is easer to use, but a bit more expensive.
I have received a sample from them, already made a video which is awaiting approval (should be online soon).
I always give commercial companies the chance to preview a video about their products, to give them a chance to clear misunderstandings. This one came out glowing, so don't expect much critizism.
Anyway, it worked great. I made 100 rounds of 16 mm balls in no time, from scrap lead that I got for free. I did use a Lee melting pot, which speeds up the procedure as you just pull up a lever and the lead pours into the mould.
I do confirm that casting lead bullets is somewhat addictive.
Lead smoke is dangerous indeed. It usually stops smoking when it is molten, though.
I did the casting outside, in fresh air, and of course I did wear safety glasses, a long sleeve jacket and gloves. I also had a fire extinguisher close by. All these safety precautions are shown in my video.
If you are worried about fumes, you could place a fan in such a way that any fumes from the pot are being blown away from you. Even though I always cast outside, I often use a fan. But if there is a fan blowing near the pot it can take longer to heat up
Lead is obviously toxic but exposure to it can be minimised with a few simple precautions. And when it comes to shooting your slingshot, lead ammo is safer than steel as it ricochets less.