I am currently gaining weight and with success!!!! I am so happy that I ve found HCRV diet. I lost a lot of weight being just raw vegan and since middle of July this year I started eating a lot of fruits ,even not knowing about 80-10-10 diet I just followed my body and with a help of watermelons, strawberries, melons, cherries, pears and apples, etc. I've got much, much better. Even I think that towards the beginning of European New Year I'll be fine. I eat app 3000 kcal a day , but I am not very active, just one hour of yoga and some walking from 45 min till 3 hours a day ( depends on a day, how busy I am) . I eat mostly mono meals whenever I want :)
My own experience was an awesome one in this regard. I came to 811 with a BMI of 18 which is officially underweight. I'd tried everything in the past to put weight on, but to no avail.
Literally after 3 weeks of 811 and getting the right amount of fruit calories in, I had put on a stone in weight and had a healthy BMI of 20.5 which is within the guidelines for 'Normal'. In the subsequent months after this I have continued to increase the amount of calories I eat, but my weight has not moved. It's still just right. I think the keys are to eat as many fruit calories as you can, and maybe initially don't do too much cardio while you're still trying to gain.