It took some time but I was finally able to have an extra hole drilled on my PT-1 for an ISO-5.
Notice how it is not black in the insides:
So I'm thinking whether I should still paint the new hole and inards or not. I actually tried to do so with a paint pen but it is not as nice as I would like. Should I paint the new hole flat black or not? If yes, what is the easiest way to do so? Note that flat black metal paint is not easily available in cans at Ace or True Value branches. If I do not paint it, will the unpainted portion tarnish and corrode? What do you guys think?
Eventually, painted or not, this is how the PT would look with the extra PSU.
I would like to point out that the extra hole is exactly the same size as the original holes. The now middle hole is equidistant to both holes which will allow the use of a Pedal Power 2+'s aux AC jack as well. In my case, I will just need to swap the ISO-5's position to a PP2+.