I started UD2 around 16-18%. Did about 14 weeks total not including two, two week diet breaks and got to 8% the last cycle from 10-8% I lost zero lean mass as "confirmed by separate dexa scans at the beginning and end of the last 4 week cycle. Lost about .7% per week
I actually really enjoyed ud2 and started it early because RFL while effective wasn't giving me the wieght lifiting volume I wanted. I could have got to my goal a lot sooner but I really wanted to start.
The first 4 week cycle I was spilling over on carbs and side effects I think were probably due to being too fat for the way the program is written.
Anyways it does wear on you and you will find it's not somthing you want to stay on. In the future I personally am going to use it as intended. Enjoy it while I have to use it but not grind through the program for months.
I think it's wise to approach it more as a tool than an all encompassing dieting strategy. I think 12% is probably an ideal place to start. A nice hard and fast 4-6 weeks to get to 8% or so. Just my thoughts