Polpentre a Loft Railway

I have a couple of hobbies, one of them being railway modelling. 

I live in a former semi detached council house built in the early thirties. It has a boarded loft and I have insulated the eves. Being eighty years old the roof area is not full of trusses.  There is however a 7"x 3" beam cutting the space in half just over 4' above the floor supported by a vertical post of a similar size. Around the roof angled at the roof pitch there are horizontal beams of 5" x 3". The two halves measure (and now I'll go metric) 3m x 2.5m and 3m x 2.2m measured at the top of the beam

You have to use the space you have, however this space is also my workshop and general storage area so there are compromises to be made. From time to time over many years I sketched different layouts. I can't remember at what point I decided to both go over and under the beams but after taking measurements found lots of 1 in 25 gradients. I decided 1 in 40 would be my maximum and looked again. This time by boring a few holes in the beams and in one place removing some wood from the top of a beams I could get much more reasonable gradients. As you might imagine I did this very carefully. I sleeved all the holes with steel tube and added strengthening steel bars and extra wood.  Five years after I cut my holes there has been no movement or splitting so I'm happy my roof isn't going to collapse anytime soon.

The main feature of the layout apart from the gradients is that the main terminus is on top of the fiddle yard so making one man operation easier. Another feature is that there is a double track all around the edge of my space. 

As I said the layout has to share this space so one immediate problem that I tackled five years ago was that the party wall was full of chimney breasts and cupboards so what I did was construct a 2.4m long rectangular tube (parallelpiped?) out of chipboard etc to take the two tracks from one side of the layout to the other and change the height by around 4cm. I then fitted the cupboards around it but one cupboard (on the lower right of the photo) actually hangs off the front of this '400 yard tunnel'. More or less that is how it stayed for the last four years.

Some photos I think