Agreed on wanting a tire diameter match, but as front and rear are different you either compromise between the two or carry two spares. That goes for an inflatable space saver too.
I don't know what wheel/tire combination you are running, but that 145-80-16 is 25.13, there are others out there that might match better, that was just one example.
I'm lost where you are going with this as you posted you wanted to cut a 7" wheel to make a 4" wide spare? Well that Marquis is a 4.5" width wheel (or choose any other compact spare of your choice), put whatever collapsible tire you want on it?
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