When you observe an H28 which has been designed with soft / slack bilges aft and then include the fact that most have had a motor, which weighs between 100-215kg (20hpBukh) installed, add 2-3 people you end up with a potential combined weight in the back of the boat of between 280- 450kg. This causes the boat to squat with the bow raised just enough to affect the ability to point.
To help counteract this most boats have their water tanks installed under the forward end of the port and starboard bunks, and I would keep these full.
The first thing I would do is check how your boat sits in the water with no one on board. Your water line should be a good guide here. If she down by the stem and you know your water tanks are empty then fill those first. (See the note above). If they are full, then using 201tr water containers trim the boat to her lines.
The easiest way to check if you need additional weight forward is to go out on a day with a nice steady breeze and your normal sailing crew in the cockpit, find an area with no tidal flow and with 1 -2 extra crew sitting amidships. Set the boat up on the wind as you would normally do, noting position of the boom, genoa cars, how much tension is on the back stay and the kicking strap. Next take a compass bearing on the land ahead and note how close to the wind you are pointing.
Staying on the same tack, now send one crew member forward at a time to sit or lie down on the fore deck at the cabin front, (the cabin front is nearly straight above the front of the keel and weight here keeps it out of the ends of the boat) Check and note the changes in pointing ability. When you have the best windward pointing, repeat the procedure on the other tack, always keeping notes.
Put the crew that were forward, on the scales and note the weight.
This total weight should be added to the boat around the V in the bunks and would include any trim ballast. Lead ingots are good for glassing in under the forward bunks. This is all trial and error and you may find that your boat is trimmed fine and weight forward makes no difference at all. If this is the case then you will need to look at the free engine power train "the sails"