I have not, but I use leather as you do....as a solid base for an overgrip. I have been happy with the TW leather grips.
I use the wider/thicker (25mm x 1.5mm). I see that the Gamma is about the same price and it appears to be about the same width, don't know about thickness.
Microgel Radical MP (5), Cheap 16g Gut/ RedDevil 1.19 - 56/54# (among other setups)