If it helps I have never had pee at the bottom of the cage
What helps there is the house being on legs rather than on the base of the cage - with the litter tray inside. The only area of pee is where the litter tray is - if they miss eg. And with hemp mat under the substrate as well it would soak anything up if the substrate didnt.
With putting the house on legs with the litter tray inside I have only had short legs so the house doesn't sit too high up. Long enough for a good space underneath the house in case they try and tunnel under it - maybe about 2" legs. I did get the rodipet legs once that slot onto their houses, but I cut them down to the size I wanted - which means needing a saw as they are quite chunky. It was almost easier just using the wood dowels I used before - I could cut those with my little saw that is not much more than a bread knife! And then just glue them onto the outside of the house.