Hi,I just started thinking about the idea of doing a preliminary pressure test on my hull (when it's made)by fitting a vacuum pump to the outside. This would be done on the bare hull but with the dome view port in place.I would need to have a negative pressure of 250 psi.Does this sound reasonable? Are there cheap vacuum pumps that can produce this negative pressure or are thereair pumps that I could modify & attach the intake to the hull ???Or has anyone done this?Regards Alan