Most MK2’s are overweight. They often are in the 220+ kg region. But remember this is the weight of the bare hull. You need to add the weight of the rig, sails and equipment and we all carry too much gear 😥 (Think anchors, engine, petrol, poles, spare ropes and what not). Then add the trolley and some contingency to make sure not to overload the springs. Overloading is far worse than a soggy trailer. An overloaded spring does not work any more and every bump in the road is directly transferred to your pride and joy’s hull. Also note that while cornering a lot of the weight shifts to one hub and spring. I think 500 kg is a better choice for your hubs and springs (250 kg each).
Cantilevered springs (rubber) / hub combinations are available everywhere for little money. On my trailer they bolt under using 4 bolts each on existing mounting plates, a job easily done yourself in an hour or so. Bring the old hubs along to compare the holes to the new ones to avoid having to drill new holes. I would prefer a caravan or builders-trailer specialist. In my experience suppliers with ‘marine’ in their name are often twice as expensive while the materials are exactly the same.