It's a good question, and I apologize that my response was delayed.
In the example you provided, the word "inch" is a word and so should be transcribed in UEB. So, your first suggestion, to use the one-word switch indicator for each "inch" is the one that I would choose. If you do not transcribe "inch" in UEB, then it could be argued that you've treated it as technical material, a sort of "i times n times c times h" instead of treating it as a word.
Thank you for your question, and thank you sincerely for providing a shot of the print.