I’ve usually found that the piano is too loud for whistle to play with, unless the piano is being played softly. But yesterday, I played my Hoover Whitecap, with piano, during congregational singing in church. I used a Dynamic instrument mic.
Did the congregation mind you taking yer shoes and socks off to play the piano? 
I don’t want to know how else you played them both at the same time.
Would that I had played the piano with my toes. 
Not if you’re playing an Overton or a Susato, or any decent wide-bored whistle.
I’ve been finding out that many high-D whistles will stand out just fine over other sounds. It doesn’t seem like it to the player, but they carry clearly for long distances.
I’ve got Aodhan’s Alba SE on loan right now. When I heard him play it at the renaissance faire in one of the most crowded areas, it seemed to be the loudest whistle I’d ever heard. Now that I’m playing it, however, it really isn’t actually that loud, it just projects.
But it was a Hoover!
Have you considered trying a Eureka? Or maybe an Orek?
I just acquired a wonderful upright Bissell. My neighbor purchased a new Wind Tunnel and was tossing her old vacuum. It was an interesting sight: that Bissell protruding from the Hoover box sitting out with her trashcans.
Now back to playing piano and whistle simultaneously.
Mack