I have taken 60 mg many times. I would only take 60 mg for a few days before I would taper to a lower dose. Yes, insomnia was a big problem at that dose.

Why are you taking that high of a dose for PMR? That is a GCA dose ... not a PMR dose. Ask your doctor but I found that a split dose of prednisone really helped control inflammation better and helped me sleep better too. I took 40 mg in the morning and 20 mg in the evening.

Splitting any dose so that it was 2/3 of the dose at 4 a.m. and 1/3 of the dose at 4 p.m was what I did. Pain would wake me up at 4 a.m. so I didn't have to set my alarm. I think it was my body's way of letting me know it was time for some cortisol.

Circulating cortisol levels should be at their highest at 8 am in morning. Taking the larger portion of your prednisone dose between 3-4 a.m. will result in your cortisol level being highest at 8 a.m.

There is a secondary smaller increase in circulating cortisol levels at approximately 6 p.m. Taking the smaller portion of your prednisone dose at 4 p.m. will cover that secondary increase in your cortisol level.

You really can't replicate the cortisol release that your body does when we aren't taking prednisone. The body's natural circadian release of cortisol is extremely complicated but the following begins to describe it.
https://www.healthline.com/health/cortisol-and-sleep
When I took high doses of prednisone, it seemed like I had no need for sleep. Eventually sleep deprivation took hold and I slept 24 hours. I also took some benadryl before going to bed and that helped me sleep..

Taking prednisone disrupts the circadian rhythm of many bodily functions. Insomnia didn't last the entire time I was taking prednisone. The body has an amazing ability to compensate for all the bad things we do to ourselves. Hopefully, when you maintain a lower stable dose of prednisone - insomnia won't be that much of a problem.