Alright, here's another product: GAF Storm Guard, $87 for 200 sq ft.
https://www.lowes.com/pd/GAF-STORMGU...yment/50353100
It's supposed to be for wind-driven rain.
I'm using GAF Timberline HDZ shingles on the whole house. Don't forget that shingle companies prefer that you use their underlayment for the warranty. I admit I'm looking for a cheaper alternative to Grace Ice and Water Shield. I'm not sure my humble Taj Mahal is worth Grace IWS.