Well...... everything has a learning curve and I'm just starting mine with acrylic. My first attempt was small. After being in the pressure pot x3 days, and just like David said, the acrylic will shrink. Well about 25% shrinkage and the round vessel is now oval too. I placed another plastic insert for the middle to hollow and I can't remove it with air nor the project, cutting and turning it will be in order. I'll be working on another project in a couple days and see if I learned anything from this project. I need to try smaller items until I can get the process down just right so I'm not wasting epoxy.