Parallel Looper Issues

[spacecommandant]

I've been working on a parallel mixer with optional tails switch. I modified the switch wiring from Induction's tails mod from the All-Star Digital Reverb, and incorporated the circuit grounding of the sends/bypass from Slacker's looper.
This version is currently working, although after plugging in power there is an initial large pop sound when either the On/Off switch or Tails switch is engaged. After waiting about 20 or 30 seconds after clicking either of these switches the first time, the switches no longer pop. I'm wondering if anyone has any ideas for eliminating this popping sound. Would it be worth trying JFET bypasses?
There is also a soft hiss in the background when engaged; what I'd describe as white noise. It's not super loud but it is noticeable at loud volumes. I'd like to reduce it as much as possible.
I'm also wondering if the 330k/47k resistors in the feedback loop of U2 are too large... those could likely be reduced, keeping the 7:1 ratio?
Any other insights and feedback for improvements would be greatly appreciated... thanks!