Mine is with engines located under the bunks. It was my request and got Levranos blessings. In fact, all boats after mine have done the same. Even some older boats chose to modify and move their engines from the aft to under the bunks. The impact on the trim by centring the load improves the performance considerably. Another advantage is the ability to
work on the engines while sailing. With big seas behind, it is impractical and dangerous to keep the aft open in case of need. Some boats I know install washboards.
I believe that engines behind have sufficient service space though I have never tried it. I prefer the access under the bunks.
One aft section is used by me as a
diving room (compressor,
gear and tanks) and the other as
storage.
As for the 75 hp, the one boat equipped with 75s that I know was 2kn slower than mine with 57s (probably because the engine was located aft and they chose to follow KYC advise and use fixed props). A boat with a clean bottom with 57s easily reaches
hull speed so I do not see how the 75 helps.