Are these screws okay for securing tub flange to studs?

[DragonBallz]

Are these screws okay for securing tub flange to studs? Or do I need the countersinking kind? This is a Kohler Underscore tub.
I'm going to need to use 5/8" backerboard because the Kohler tub flange is so thick.

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[Breplum]

We NEVER drill through tub flanges. That pic of your tub is not so much a flange as a full lip. Doesn't even look like it is designed for tile. We only use flat stainless steel washers and low profile washer head screws.
I would furr out flush with that stupid lip and do as I described. These GRK fastners are great

 

[Sponsor]

 

[DragonBallz]

We NEVER drill through tub flanges. That pic of your tub is not so much a flange as a full lip. Doesn't even look like it is designed for tile. We only use flat stainless steel washers and low profile washer head screws.
I would furr out flush with that stupid lip and do as I described. These GRK fastners are great
View attachment 80778

Thank you. I will change the screws.

This is the tub.

https://www.us.kohler.com/us/underscore-60-x-32-alcove-bath-with-integral-apron-integral-flange-and-left-hand-drain/productDetail/bathing/1267894.htm

 

[Terry]

I have used lath screws, I hope those were okay to use.

 

[John Gayewski]

I don't mind the self tapping lath screws. Stainless ones would be the best in my opinion. If you can find stainless steel self tapping lath screws you'd be in business. Probably wouldn't hurt to coat the screws in silicone caulk before they get drilled.