I belive you could install peace of 0.5mm thick thermal pad and everything will be fine.
But manufacturers of waterblocks know very well.
Is it ASUS RTX2080 Dual reference PCB.
I strongly suggest Watercool Heatkiller blocks.
I talk about build quality and performance.
Only real representation of famous German quality.
Germans are specialists in working with metals.
They are build in Germany, as they say on last machines for cutting metals and I didn't hear on complains on their alloyes corrosion.
Special is best combination of CPU and GPU block of same type bare Copper- bare Copper, Nickel Plated Copper-Nickel Plated Copper.
This year Watercool.de build waterblocks for ASUS RTX2080Ti Strix.
That's nice advantage compare to other brands, special for people who met with Heatkiller quality.