Thanks everyone for your help. I have decided to go with a straight loop keeping it as close as I can to the edge of the ply sheet and leaving as much room as I can in the centre. Unfortunately the 'L' shape was going to occupy too much of area. I already have a monorail with a loop at each end, climbing 2x regular height which takes up roughly half the board and now the train will encircle it.
The theme of the layout is an environmentally friendly one, the train will collect trees from the plantation, deliver them to the monorail which climbs the hill using 1 carriage to carry the trees to revegetate the hill and 1 carriage for the workers. Other items I want to build will be a dam for hydro electric power, wind turbines and a solar farm (not sure how to do the panels at the moment). Also some high density housing, lots of bikes, recycling truck and bins and anything else I think encompasses the future I'd like my kids to enjoy 😃