locoworks

depends on you curve radii, buffer beam mounted needs gentle curves

with coaches ( the older farish ones i converted ) i spun the bogies and removed the coupler and spring and then fitted the DG coupling to what was the non coupling end of the bogie. with loco's as the box is in 2 halves by design it is just a matter of making the coupling the correct shape to fit the box.

'a bit keen' = wants it finished yesterday

stick with N, there is no need to use all the space you have anyway. the bigger things get the more expensive!!??. i would built the layout as a stand alone item with no permanent fixings to walls or floors so it could be taken to exhibitions. not necessarilly to take it to exhibitions, but so it can be dissasembled ( make sure baseboards can fit through the loft hatch ) and erected elsewhere if you move.

as you are using steamline trackage i would change the storage loops at the top so the 2 points on the left are right hand and the 2 on the right are left hand/ the actual curve of the point completes the curve/arc of the loops nearer the backscene and then a curve is put on the straight exit to briung things parallel. doing it this way removes all of the reverse curves in the storage area and makes the loops sligtly longer. there is no need to complete the curve in plain track and then fit points on the straight bits. you could even use curved points instead, but you may want the track seperation that the straight points will help with.

you would need to go down the route of slips and/or diamond crossings.

that salt lake route american plan is almost identical to the 'salt lake route' that used kato N track in recent issues of model railroader. the kato track version uses the twin mainline trackage for the scenic part with super elevated curves.