Although I am a dedicated DH diver, I've been looking for a USD Calypso IV regulator for sometime to rebuild for fun. Recently I found and purchased a Calypso IV on EBay. It was in pristine exterior condition and at a great price. It only had mild corrsion inside the 2nd stage. Vinegar and a green scrubby took care of that. I then bought the 1st & 2nd(1085) rebuild kits from Bryan. Once apart, I found the regulator did not have the castle seat bushing from the recall update 1979. I ordered one along with the rebuild kits. I rebuilt the regulator and set the IP for 130 psi. I discovered it had an IP creep from 125 to 140+ psi. After several attempts to surface the soft HP seat, the IP continued to slowly creep up. I took it apart and took out the brass cone from the seat and switched it to the other side. After flipping the HP seat and putting in a new master spring shim --Bingo! The IP pressure locked and held at 130 psi. I cycled the reg for about 75 cycles and it held there through the night. I now have a great looking & working Calypso IV to play with. It will now join my single hose fleet of SP Mk2, Mk5, and my beloved Cyklon 300. Thanks Bryan for your instructional video on the Calypso IV, it was very helpful on my rebuilding project.