I mostly do 1:20.3 but there is some great stuff in 1:29 and 1:32. How do you handle the differences in structures etc?
I would place the 1:20.3/1:22.5 strcutures in the forground and place the 1:29/1:32 in the background to create a forced perspective. Depending of the location you could even place O gauge structures behind the 1:32 structures to give an added dimnsion of depth but its critical on the location of the vista that it look like its natural. In otherwords a flat town grid will not work with this idea but a hillside town where the building stack up behind each other would work very well.
Remember too that some structures prototypically come in varying sizes, so you could mix some in that way. Things like warehouses and shacks/shanties don’t have one “size,” so you can use different scales to represent different sizes.