We have made some progress with Grendel this year.
After years of basically letting her be, we became more intrusive this year--probably as a result of Fat Sally's death. We didn't want any hidden health problems to crop up when it was too late for us to do anything for her, so Grendel got hauled to the vet several times this year.
She is passive for a feral. She will let me pet her if she can't escape but then will sneak off to a new hidey--hole soon after. Catching her to take her to the vet has become progressively less traumatic though we still have to corner her and stuff her into a carrier against her efforts to escape. But then, there are several nominally "tame" cats that have to be treated like that, so I'm not holding that against her.
Grendel has to be about eleven or twelve now--a round-bodied tortoiseshell with golden eyes. She is virtually invisible most of the time. She and Skinny (aka Star) have a large cardboard box hideaway in the corner of our main upstairs room. If the house is quiet--after I go to work or town or after bedtime at night--Grendel comes out of her den and will go downstairs to sleep on the bed of the spare room, desirable because of the access to the outside cat condo from there. When the weather is fine, she likes to sit out in the condo and watch the birds and take in some sun.
Her fear of us is slowly eroding. She watches us warily if we enter the room when she is exposed on the bed, but doesn't run for cover every time she sees us. I try to peek into her den and say "Hi" frequently, just so she will get used to our attention. It's a quiet life but she seems happy, with shelter and companionship and a steady supply of food. I hope some day I will wake up to find her sleeping on the foot of my bed, but if that never happens, I will still feel we have done okay by her.