The use of the 1590a for the Hysteresis Oscillator was out of necessity rather than any aesthetic purpose. I had limited space on my board but had to get the pedal on there somehow. To be honest, I could probably have gotten away with housing it in the next size up, but I had the enclosure lying about from a previously aborted build and thought, 'Ooh...'.
When the time came to fit everything in, the caps I'd used where quite large and were touching the output jack. This left the board proud and the back unable to bolt in properly. I removed them, bought some small (very small) caps and voila !! Overall, the build was a pain in the arse from beginning to end, but I love how it looks and sounds. It also seems to pique peeps curiosity due to it's diminutive apparel.