I see you ran into the 17/32" drill bit as well, I ordered my rockers and fenders from Metalcloack and found out I needed it when reading the instructions, had to order from Amazon as well. Being that is not a common size it would make sense to include it with the hardware kit, another $10 added to the price won't make any difference.
I was toying with the idea of clear coating my aluminum parts as well, and when doing some research I found mixed opinions, some say the clear coat will peel, others said the aluminum will become dull under the clear coat. In the end I decided is not worth the risk to experiment, so the rocker guards will be painted silver to match the Jeep and the sliders and fenders in black.
2004 Rubicon (auto), 4", TW 1350 CV shaft, Skyjacker High clearance transfer skid, 35"s...
2016 JKUR (auto), 3.5", Artec AL armor, MC fenders