The urine tray is the heart of a kiwi bog. As you can imagine measurements must be precise for it to effectively do its job. The faeces hole may appear too small but is in fact more than sufficient.
you need to feed your urine somewhere. Most of our customers use a soak that is a hole in the ground recovered with the sods removed to dig the hole. The hole should contain gravel rising up through small stones to larger stones near the surface. You should run your urine outlet pipe in just below the surface so the urine trickles down slowly before being dissipated though the gravel then the earth. The hole should be about a meter cube. The hole itself should be below the urine outlet so the urine is carried by gravity. A cubic meter is an adequate size for a soak. Most councils require the hole to be at least 80 meters from running or standing water. But some councils may allow closer. Other options are to store the urine and dispose of it separately. It may be possible to crystallize it using a glass pain and sun power. Some people add the urine to their other household water and feed it to water their garden. There is also a water filtering system that cost about the same as a bog and has filters that can be cleaned out. I think I have a link to it here (see links). The pipe fittings you need are 32mm sewerage grade pipe from your bog to your destination as above. You can buy 32mm saddles to mount your pipe if you need. Pipe and fittings are available from any plumbing suppliers or Bunnings or Mitre10. You need a 32 to 40mm adapter and a 40 to 65mm adapter (that looks a bit like funnel - make sure you get the right one because there is another sort that is not suitable) which you mount below your urine tray so that the 65mm goes round the urine outlet but does not touch. This allows you to remove the tray for cleaning without removing the drainage system. The tray outlet is around 40mm. A 20 litre bucket can hold around 60 defecations. And weighs less than 20kg.