We have an 8 road fiddle yard which will accommodate anything with 16.5mm gauge track e.g. OO, HO, ON30, 7mm NG, EM.
Currently it is being used to support Purgatory Peak (ON30) and the New OO.
It has two 5ft x 3ft corner boards with all the pointwork.
Currently it has two 4ft and one 4ft 6in intermediate boards which just have 8 roads of straight track.
All, some or none of these can be connected or new straight boards can be built to give the length needed for any given layout.
It means that all you need to do to build a new layout is build the front scenic boards.