So you're getting a non-taxable gain of $3.50/SIAF share in the US? Doesn't make sense.
What I read from your rules, in the US, is that stock dividends usually (like this one) is not taxed. But this is not a stock dividend IMO. It's a spin-off.
I should be telling you now to get some professional advice on this. And that is what the company will do. But I think that's how it will play out. And then $3.50 becomes the basis for when you sell your Triway shares, so you don't pay tax twice.