Walking Harness for Older Cat

I am fostering a cat that might become a permanent member of my household. Poncho is 11, neutered male and about 5 lbs overweight. He enjoyed being able to go outside on his own up until about two years ago at his former residence. As he is in a new home and neighborhood, I'd like him to go outside but am considering a harness.

I already have two cats that do go outside all day but must come in at sunset. We are all used to this routine. I am not comfortable letting the new guy out on his own at all. I cannot build a sheltered pen where I live. On top of that, we all might be moving in November.

Has anyone used the harness on an older cat? What happened?

I have trained both my 9 year old cats in a harness (trained them at 7 when I got them). They aren't allowed out unattended, if anything attacked them and they couldn't get away I'd never let myself live it down, but I attach them to the clothesline when I'm outside and it has worked out quite well! They actually have learned to like the harness, because they know that means outside time.

You can harness train an older cat, and Figure H harnesses is especially good if he's uncomfortable (no need to slip the cat's head or leg through-it just snaps together).