Raft and jackets are essential in my opinion, but the real clincher for me is how I feel about my engine. It's been running flawlessly with very consistent cht/egts, oil temps and pressures for quite some while, so I have gradually felt more comfortable about it and tried longer sea crossings. I would recommend that you try newtownards via the short crossing from Stranraer/mull of Galloway and then build it up from there. Oh and make sure you are talking to someone. Fisbang and his mates at Scottish info will be quick to get someone out to you if they know you are going down.