varathane
smallfly:
I have had very good luck with Varathane Super Diamond Floor Finish. Works for me with nitro of 10% and 15%. Comes in Gloss, semi-gloss and satin.
This stuff is hard as an old boot. I also use it for glassing in place of epoxy.
Locally, Lowe's sells it but I have only seen it there in gallon cans and it is rather expensive (about $38-40/gallon). I know it is produced in quarts but I have never seen them.
I got a gallon from a friend a couple of years ago who, at that time, was "in the trade". Think it cost me about $25.00.
I have heard of people having good luck with Carver-Tripp but I don't know that specifically.
I have had the same experience as you with MinWax.
My experience. "Your mileage may vary".
edit starts here:
You would normally NOT expect a clear WATER based Poly-U to yellow. Oil based would (or should) be the culprit here as most oils used in Poly-U formulations tend to be on the "yellow" side themselves.
Dan