6 hours ago, Keith Addenbrooke said:

.....Could I ask if you k ow what height you plan to display the layout at - if it’s eye level the arch may not need changing (or only a bit) as you’d be looking up at it, but if it’s for showing at a lower level then yes, I’d suggest increasing the height as taller folk  may not see much layout....                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

Thank you  for leaving the comments guys.

I'm thinking of around 4 ft 3 inchs  as the track bed height above floor level. The height of the arch above track bed on the 1/8 scale model is approximately 12 inches. I don't know why I made it this high as I'd created the diagram below for a previous layout and should have taken note. So the arch needs to go up at least 2 inches so that there will ba a gap of around 14 inches between the track bed and the bottom of the arch facia.

The cassette board end panels will be the only solid upright pieces on the model. The arch will rest on these panels at each end. My intention is to use lockable hinges on these panels so they fold down for transportation. This means they will be added at a later stage of baseboard construction so I can play around with the arch height during the building of the layout.