I would start with a few WiFi SSM’s, spread them around the house (target locations) and then experiment for a day of so. A sheet of foil held up by two sticks, themselves stuck into globs of plasticine. Move 'em sticks and map the response at the target locations. Eventually you’d get a sense of it and would start optimizing, me think.
And I certainly would not worry about the legality of the set-up, there is no way you would get any kind of gain that would suddenly put your registered/tested WiFi router in the Canadian-FCC-equivalent’s bad book. Plenty of losses, but gain? Nay. Targeting is the objective.