IP as a Blue Water boat
We had a '69 Bristol 29 for 10 years. It is a solid, well built boat with a 4'6' draft. We always felt very safe, but a little small to go off-shore cruising for extended time.
In 2005 we bought a used 2004 (in the water for 2 months) IP 370. Having never sailed on an IP, we still made the decision to go the IP route. We have never doubted our decision. The boat is heavy, extremely well made and very roomy. This is typical of all IP's.
Would I feel confident going off-shore? I would first have the boat and it's systems completely checked and made ready for the rigors of blue water sailing and then absolutely be comfortable in my decision.
Hope this helps your decision.