Customizable Gutter or Pipe Adapter for Round to Rectangle

So, at our makerspace's new building we found we had puddles which weren't good, and happened to have some 4" flex pipe, but the drain is a 4" by 5.5" pipe coming down.

So here's an adapter, which should be customizable either for Round to Rectangle or vice versa. Set the circular_use_id (Inner Diamater) to choose which to use. (Rectangular, just enter the dimensions (-2*wall thickness) if you want it to go on the inside.)

Anyway, I hope this is useful to someone, and to us (as it hasn't yet been printed.)

Edit: 2024 March 5: Added -3 which corrects the centering if you adjust the thickness (It wasn't correct with the 2mm thickness, but I never noticed. Ministry42 pointed it out.