Stability of floating dock

Making a 6m x 2.45m floating platform with an Aluminium Deck, and an office that is 4.5m long and 2.4m wide, centrally located on the platform. My total lift is 3690kg and if I only use 50% of that as a safety, then with the following (Salt Water}: Deck 500kg Drums 190kg Office 400kg People at one time Max 8 at 80kg each 640kg. Total weight 1730kg 50% for safety is 1845kg of lift. Each plastic drum has a circumference of 185cm (Drum width 59cm) The height of each drum is 92cm. 3 rows of 6 with the outside 6 being level with the outer 6m edge of the deck. Drums are laid lengthwise on their side. The level deck is 10cm above the top side of the floats. Office is moved to centre. One 6m side is tied to the walkway. The Marina is fully enclosed and swell is not an issue. In the event of Cyclone the office unbolts to lie flat on the pontoon. I really need the top of the deck to float near level with the walkway at 40cm above the water, so need to know where the above will float at.