Yes the B28 was a later design than the B24. But not by much.
The B28 was not a "Stretched" B24, but incorporated all of the B 24's good features. It had a comfortable and protected cockpit. It would sleep 5 in comfort.(three singles, one double). The double being the cabin bench seat folded down.
With a crew of five we would sleep on the boat at a visiting yacht club.
IE:- We would race across Lake Ontario to a club on the American North shore, stay the night aboard and race back the next day.
On overnight races with four crew, there would be three in the bunks and one on the helm, taking two hour watches.
Of course it didn't always work out that way.
I remember in one triangular overnight race across Lake Ontario, I was on the helm all night whilst Lock Crowther, Logan Apperley and my wife Jillian were all in Bye-Bye land. I took to my bunk in the mornings light and so missed out on all the interesting racing sailing that occurred during the rest of the day.
It had a proper galley, with plenty of food storage cupboards, A proper toilet and "walk thru" feature to the bow bunk area. The centreboard trunk was incorporated in the front of the cabin bench seat and so did not intrude on cabin space. A 10 hp outboard motor was mounted on a standard lifting bracket on the transom and was great for no wind/flat water motoring, but was no use in a windy chop. It was much better to just sail the boat.
Under reefed sail we survived one wild night where other boats lost their rudders, masts and one boat actually sank.
Over the years I have built, owned, cruised and raced seven multihulls---but the B28 was the best of them all.
I just wish I could get my hands on a set of B28 plans. I would make them available once again, as I have done with the B24.
If anyone has a set of B28 plans left over from building ,even if they are in rough shape but capable of being restored, then please PM me. I wiii pay good money to buy or lease them.