I’m sorry your stamps and models aren’t looking the way you want them to.
It sounds like the cube that you sculpt in is way too big. If you look around within MasterpieceVR, you should see the outline of a cube around you. Try shrinking that down a bunch before converting models. You can shrink it down with the grip buttons on your controllers.
Another thing you can try is changing the resolution of that cube. At the bottom of the Create menu, you should see a part that says Cube Properties. Click on that, and increase the resolution a bit.
Hope that helps! Let me know if it doesn’t.