Hal,
Geez, you got me on that one. The foil isn’t a bad idea at all, but, I haven’t tried that. What about parchment paper? I guess, were it me, I’d step the heat up a bit from what you are used to, leave the pieces unwrapped, so the fat can cook out, put my digital meat thermometer in the middle of the breast, and pull it out when it said 125-130, letting it rest for 15 minutes.
A roasted snow is a rare treat in my part of the world. Hope it goes well. Snows must not spend as much time digging and eating mollusks out of sewage lagoons as Canada’s do.

Best,
Ted

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Facing Windsor.