I don't know about fan designs, but there was a role-playing scenario book that had an experimental ship in the Exodus fleet mis-jump to a time circa the Clan Invasion. Forgot the name, since I left it with a bunch of other such books at a friend's house. It had full deck-plans for that ship.
Edit: Living Legends?
You are correct! It was a
Manassas Heavy Cruiser that had the experimental Jump drive to let them go 40 light years at a time. In their last KF Jump, it took them to their destination system, but they needed 274 years to arrive.
The book
Living Legends had the warship layout in the very back, in pages 58-64.
If you want a thread that discussed the Manassas, its jump drive, and a few potential implications,
here it is