Here are some responses to Mohammad's questions:
1. I have a Honda 20HP outboard, which is quite heavy (but the same weight as the 15HP). The boat behaves well with it - no issues.
2. I can plane with 4 people in it but not too much luggage. This was my objective.
3. I don't think I have any options - unless the 2 lockers upfront are an option. One of them is for the gas tank and the other for the anchor. Work well. Maybe it would be nice to have a cleat for the anchor line.
4. No issues. After 3 years of trying to get the dinghy to stop swinging around and the engine throttle taking the load when sailing on starboard tack (because the dinghy slides over when the boat heels), I now have very little movement. I also have 5 cm wide belts as tie downs.
5. Yes, on the 55 the dinghy fits perfectly sideways in front of the traveler and behind the mizzen.
I first saw the rounded dinghy stops on the davits of Fortuna II, Paul Brown's boat. I modified them to give a few cm more space between the davits and the dinghy because the strops would otherwise have bottomed out against the davits. If you have different lifting strops, you can have the space reduced which brings the dinghy marginally further up.
I hope this helps.