Thanks, All good stuff.
I got a bit sidetracked with Ed’s comment about TLRs using square because it’s difficult to change the orientation on them so I looked into why TLRs were designed like they were. Then I thought about the mathematics (aesthetics, permutations) of cropping S->R vs R->S (R = rectangular) and I’m still unsure about that but it’s good to know, by and large, anything goes.