Just had a look through your posts and realised that you have a 3m sib.
While the boat and engine you have got are both excellent, IMHO a trip to the IOW in it is a little ambitious. It can get very rough in the middle of the Solent and the wakes from ferries/Big Mobo's/ ships are going to cause you significant issues.
You really need some training 1st and also basic safety kit, including a radio.
I don't want to be negative, but there are lots of places you can go on this side of the water, wait till you get some more experience and a bigger boat before you 'go abroad'
In reply to your question, when rafting you must always tie your ropes to the pontoon, not your neighbor.